MC9S08QA4
MC9S08QA2
Reference Manual
HCS08
Microcontrollers
Related Documentation:
• MC9S08QA4 (Data Sheet)
Contains pin assignments and diagrams, all electrical
specifications, and mechanical drawing outlines.
Find the most current versions of all documents at:
http://www.freescale.com
MC9S08QA4RM
Rev. 2
3/2008
freescale.com
MC9S08QA4 Features
8-Bit HCS08 Central Processor Unit (CPU)
•
•
•
Up to 20 MHz CPU at 3.6 V to 1.8 V across
temperature range of –40°C to 85°C
HC08 instruction set with added BGND
instruction
Support for up to 32 interrupt/reset sources
•
•
Development Support
•
•
On-Chip Memory
•
•
•
Flash read/program/erase over full
operating voltage and temperature
Random-Access memory (RAM)
Security circuitry to prevent unauthorized
access to RAM and flash contents
Power-Saving Modes
•
•
•
Two very low power stop modes
Peripheral clock enable register can disable
clocks to unused modules, thereby reducing
currents
Very low power real time counter for use in
run, wait, and stop modes with internal
clock sources
Internal Clock Source (ICS) — Internal
clock source module with a
frequency-locked-loop (FLL) controlled by
internal reference; precision trimming of
internal reference, which allows 0.2%
resolution and 2% deviation over
temperature and voltage; support of bus
frequencies from 1 MHz to
10 MHz
System Protection
•
•
•
•
Watchdog computer operating properly
(COP) reset with option to run from
dedicated 1 kHz internal clock source or
bus clock
Low-Voltage detection with reset or
interrupt
Selectable trip points
Illegal opcode detection with reset
Single-Wire background debug interface
Breakpoint capability to allow single
breakpoint setting during in-circuit
debugging
Peripherals
•
•
•
Clock Source Options
•
Illegal address detection with reset
Flash block protection
•
•
ADC — 4-channel, 10-bit resolution;
1.7 mV/°C temperature sensor; automatic
compare function; internal bandgap
reference channel; operation in stop3; full
functionality from 3.6 V to 1.8 V.
ACMP — analog comparator with
selectable interrupt on rising, falling, or
either edge of comparator output; compare
option to fixed internal bandgap reference
voltage; output can be tied internally to
TPM input capture; operation in stop3
TPM — One 1-channel timer/pulse-width
modulator (TPM) module; selectable input
capture, output compare, or buffered edgeor center-aligned PWM on each channel;
ACMP output which can be tied internally
to input capture
MTIM — 8-bit modulo timer module with
8-bit prescaler
KBI — 4-pin keyboard interrupt module
with software selectable polarity on edge or
edge/level modes
Input/Output
•
•
Four GPIOs, one input-only pin and one
output-only pin
Hysteresis and configurable pullup device
on all input pins; configurable slew rate and
drive strength on all output pins except
PTA5
Package Options
•
8-pin SOIC, 8-pin DIP, 8-pin DFN
MC9S08QA4 MCU Series Reference Manual
Covers:
MC9S08QA4
MC9S08QA2
MC9S08QA4
Rev. 2
3/2008
Revision History
To provide the most up-to-date information, the revision of our documents on the World Wide Web will
be the most current. Your printed copy may be an earlier revision. To verify you have the latest information
available, refer to:
http://freescale.com
The following revision history table summarizes changes contained in this document.
Revision
Number
Revision
Date
1
1/2008
Initial public release
2
3/2008
Changed Chapter 11, “Internal Clock Source (S08ICSV1)” to use the ICSV1.
Description of Changes
Freescale and the Freescale logo are trademarks of Freescale Semiconductor, Inc.
© Freescale Semiconductor, Inc., 2008. All rights reserved.
MC9S08QA4 MCU Series Reference Manual, Rev. 2
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List of Chapters
Chapter Number
Title
Page
Chapter 1 Device Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chapter 2 External Signal Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Chapter 3 Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Chapter 4 Memory Map and Register Definition. . . . . . . . . . . . . . . . . . . . . . . 33
Chapter 5 Resets, Interrupts, and General System Control . . . . . . . . . . . . . 51
Chapter 6 Parallel Input/Output Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Chapter 7 Central Processor Unit (S08CPUV2) . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 8 Keyboard Interrupt (S08KBIV2) . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Chapter 9 Analog Comparator (S08ACMPV2). . . . . . . . . . . . . . . . . . . . . . . . 103
Chapter 10 Analog-to-Digital Converter (S08ADC10V1) . . . . . . . . . . . . . . . 111
Chapter 11 Internal Clock Source (S08ICSV1) . . . . . . . . . . . . . . . . . . . . . . . 139
Chapter 12 Modulo Timer (S08MTIMV1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Chapter 13 Timer/Pulse-Width Modulator (S08TPMV2) . . . . . . . . . . . . . . . . 161
Chapter 14 Development Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
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Contents
Section Number
Title
Page
Chapter 1
Device Overview
1.1
1.2
Introduction .....................................................................................................................................17
1.1.1 Devices in the MC9S08QA4 Series ..................................................................................17
1.1.2 MCU Block Diagram ........................................................................................................18
System Clock Distribution ..............................................................................................................19
Chapter 2
External Signal Description
2.1
2.2
Device Pin Assignment ...................................................................................................................21
Recommended System Connections ...............................................................................................21
2.2.1 Power ................................................................................................................................22
2.2.2 Reset (Input Only) ............................................................................................................23
2.2.3 Background / Mode Select (BKGD/MS) ..........................................................................23
2.2.4 General-Purpose I/O and Peripheral Ports ........................................................................24
Chapter 3
Modes of Operation
3.1
3.2
3.3
3.4
3.5
3.6
Introduction .....................................................................................................................................27
Features ...........................................................................................................................................27
Run Mode ........................................................................................................................................27
Active Background Mode ...............................................................................................................27
Wait Mode .......................................................................................................................................28
Stop Modes ......................................................................................................................................29
3.6.1 Stop3 Mode .......................................................................................................................29
3.6.2 Stop2 Mode .......................................................................................................................30
3.6.3 Stop1 Mode .......................................................................................................................31
3.6.4 On-Chip Peripheral Modules in Stop Modes ....................................................................32
Chapter 4
Memory Map and Register Definition
4.1
4.2
4.3
4.4
4.5
MC9S08QA4 Series Memory Map .................................................................................................33
Reset and Interrupt Vector Assignments .........................................................................................34
Register Addresses and Bit Assignments ........................................................................................35
RAM ................................................................................................................................................38
Flash ................................................................................................................................................39
4.5.1 Features .............................................................................................................................39
4.5.2 Program and Erase Times .................................................................................................39
4.5.3 Program and Erase Command Execution .........................................................................40
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4.6
4.7
4.5.4 Burst Program Execution ..................................................................................................41
4.5.5 Access Errors ....................................................................................................................43
4.5.6 Flash Block Protection ......................................................................................................43
4.5.7 Vector Redirection ............................................................................................................44
Security ............................................................................................................................................44
Flash Registers and Control Bits .....................................................................................................45
4.7.1 Flash Clock Divider Register (FCDIV) ............................................................................46
4.7.2 Flash Options Register (FOPT and NVOPT) ....................................................................47
4.7.3 Flash Configuration Register (FCNFG) ...........................................................................48
4.7.4 Flash Protection Register (FPROT and NVPROT) ..........................................................48
4.7.5 Flash Status Register (FSTAT) ..........................................................................................49
4.7.6 Flash Command Register (FCMD) ...................................................................................50
Chapter 5
Resets, Interrupts, and General System Control
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
Introduction .....................................................................................................................................51
Features ...........................................................................................................................................51
MCU Reset ......................................................................................................................................51
Computer Operating Properly (COP) Watchdog .............................................................................52
Interrupts .........................................................................................................................................53
5.5.1 Interrupt Stack Frame .......................................................................................................54
5.5.2 External Interrupt Request Pin (IRQ) ...............................................................................54
5.5.3 Interrupt Vectors, Sources, and Local Masks ...................................................................55
Low-Voltage Detect (LVD) System ................................................................................................56
5.6.1 Power-On Reset Operation ...............................................................................................57
5.6.2 LVD Reset Operation ........................................................................................................57
5.6.3 LVD Interrupt Operation ...................................................................................................57
5.6.4 Low-Voltage Warning (LVW) ...........................................................................................57
Real-Time Interrupt (RTI) ...............................................................................................................57
Reset, Interrupt, and System Control Registers and Control Bits ...................................................58
5.8.1 Interrupt Pin Request Status and Control Register (IRQSC) ............................................59
5.8.2 System Reset Status Register (SRS) .................................................................................60
5.8.3 System Background Debug Force Reset Register (SBDFR) ............................................61
5.8.4 System Options Register 1 (SOPT1) ................................................................................62
5.8.5 System Options Register 2 (SOPT2) ................................................................................63
5.8.6 System Device Identification Register (SDIDH, SDIDL) ................................................64
5.8.7 System Real-Time Interrupt Status and Control Register (SRTISC) ................................65
5.8.8 System Power Management Status and Control 1 Register (SPMSC1) ...........................66
5.8.9 System Power Management Status and Control 2 Register (SPMSC2) ...........................67
5.8.10 System Power Management Status and Control 3 Register (SPMSC3) ...........................68
Chapter 6
Parallel Input/Output Control
6.1
6.2
Port Data and Data Direction ..........................................................................................................69
Pin Control — Pullup, Slew Rate, and Drive Strength ...................................................................70
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6.3
6.4
Pin Behavior in Stop Modes ............................................................................................................70
Parallel I/O Registers ......................................................................................................................71
6.4.1 Port A Registers ................................................................................................................71
6.4.2 Port A Control Registers ...................................................................................................72
Chapter 7
Central Processor Unit (S08CPUV2)
7.1
7.2
7.3
7.4
7.5
Introduction .....................................................................................................................................75
7.1.1 Features .............................................................................................................................75
Programmer’s Model and CPU Registers .......................................................................................76
7.2.1 Accumulator (A) ...............................................................................................................76
7.2.2 Index Register (H:X) ........................................................................................................76
7.2.3 Stack Pointer (SP) .............................................................................................................77
7.2.4 Program Counter (PC) ......................................................................................................77
7.2.5 Condition Code Register (CCR) .......................................................................................77
Addressing Modes ...........................................................................................................................79
7.3.1 Inherent Addressing Mode (INH) .....................................................................................79
7.3.2 Relative Addressing Mode (REL) ....................................................................................79
7.3.3 Immediate Addressing Mode (IMM) ................................................................................79
7.3.4 Direct Addressing Mode (DIR) ........................................................................................79
7.3.5 Extended Addressing Mode (EXT) ..................................................................................80
7.3.6 Indexed Addressing Mode ................................................................................................80
Special Operations ...........................................................................................................................81
7.4.1 Reset Sequence .................................................................................................................81
7.4.2 Interrupt Sequence ............................................................................................................81
7.4.3 Wait Mode Operation ........................................................................................................82
7.4.4 Stop Mode Operation ........................................................................................................82
7.4.5 BGND Instruction .............................................................................................................83
HCS08 Instruction Set Summary ....................................................................................................84
Chapter 8
Keyboard Interrupt (S08KBIV2)
8.1
8.2
8.3
8.4
Introduction .....................................................................................................................................95
8.1.1 Features .............................................................................................................................97
8.1.2 Modes of Operation ..........................................................................................................97
8.1.3 Block Diagram ..................................................................................................................97
External Signal Description ............................................................................................................98
Register Definition ..........................................................................................................................98
8.3.1 KBI Status and Control Register (KBISC) .......................................................................98
8.3.2 KBI Pin Enable Register (KBIPE) ....................................................................................99
8.3.3 KBI Edge Select Register (KBIES) ..................................................................................99
Functional Description ..................................................................................................................100
8.4.1 Edge Only Sensitivity .....................................................................................................100
8.4.2 Edge and Level Sensitivity .............................................................................................100
8.4.3 KBI Pullup/Pulldown Resistors ......................................................................................101
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8.4.4
KBI Initialization ............................................................................................................101
Chapter 9
Analog Comparator (S08ACMPV2)
9.1
9.2
9.3
9.4
Introduction ...................................................................................................................................103
9.1.1 ACMP Configuration Information ..................................................................................103
9.1.2 ACMP/TPM Configuration Information ........................................................................103
9.1.3 Features ...........................................................................................................................105
9.1.4 Modes of Operation ........................................................................................................105
9.1.5 Block Diagram ................................................................................................................105
External Signal Description ..........................................................................................................107
Register Definition ........................................................................................................................107
9.3.1 ACMP Status and Control Register (ACMPSC) ............................................................108
Functional Description ..................................................................................................................109
Chapter 10
Analog-to-Digital Converter (S08ADC10V1)
10.1 Introduction ...................................................................................................................................111
10.1.1 Module Configurations ...................................................................................................112
10.1.2 Features ...........................................................................................................................115
10.1.3 Block Diagram ................................................................................................................115
10.2 External Signal Description ..........................................................................................................116
10.2.1 Analog Power (VDDAD) ..................................................................................................117
10.2.2 Analog Ground (VSSAD) .................................................................................................117
10.2.3 Voltage Reference High (VREFH) ...................................................................................117
10.2.4 Voltage Reference Low (VREFL) ....................................................................................117
10.2.5 Analog Channel Inputs (ADx) ........................................................................................117
10.3 Register Definition ........................................................................................................................117
10.3.1 Status and Control Register 1 (ADCSC1) ......................................................................117
10.3.2 Status and Control Register 2 (ADCSC2) ......................................................................119
10.3.3 Data Result High Register (ADCRH) .............................................................................120
10.3.4 Data Result Low Register (ADCRL) ..............................................................................120
10.3.5 Compare Value High Register (ADCCVH) ....................................................................121
10.3.6 Compare Value Low Register (ADCCVL) .....................................................................121
10.3.7 Configuration Register (ADCCFG) ................................................................................121
10.3.8 Pin Control 1 Register (APCTL1) ..................................................................................123
10.3.9 Pin Control 2 Register (APCTL2) ..................................................................................124
10.3.10Pin Control 3 Register (APCTL3) ..................................................................................125
10.4 Functional Description ..................................................................................................................126
10.4.1 Clock Select and Divide Control ....................................................................................126
10.4.2 Input Select and Pin Control ...........................................................................................127
10.4.3 Hardware Trigger ............................................................................................................127
10.4.4 Conversion Control .........................................................................................................127
10.4.5 Automatic Compare Function .........................................................................................130
10.4.6 MCU Wait Mode Operation ............................................................................................130
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10.4.7 MCU Stop3 Mode Operation ..........................................................................................130
10.4.8 MCU Stop1 and Stop2 Mode Operation .........................................................................131
10.5 Initialization Information ..............................................................................................................131
10.5.1 ADC Module Initialization Example .............................................................................131
10.6 Application Information ................................................................................................................133
10.6.1 External Pins and Routing ..............................................................................................133
10.6.2 Sources of Error ..............................................................................................................135
Chapter 11
Internal Clock Source (S08ICSV1)
11.1 Introduction ...................................................................................................................................139
11.1.1 Module Configuration .....................................................................................................139
11.1.2 Factory Trim Value .........................................................................................................139
11.1.3 Features ...........................................................................................................................141
11.1.4 Modes of Operation ........................................................................................................141
11.1.5 Block Diagram ................................................................................................................142
11.2 External Signal Description ..........................................................................................................143
11.3 Register Definition ........................................................................................................................143
11.3.1 ICS Control Register 1 (ICSC1) .....................................................................................143
11.3.2 ICS Control Register 2 (ICSC2) .....................................................................................144
11.3.3 ICS Trim Register (ICSTRM) .........................................................................................145
11.3.4 ICS Status and Control (ICSSC) .....................................................................................145
11.4 Functional Description ..................................................................................................................146
11.4.1 Operational Modes ..........................................................................................................146
11.4.2 Mode Switching ..............................................................................................................148
11.4.3 Bus Frequency Divider ...................................................................................................148
11.4.4 Low Power Bit Usage .....................................................................................................149
11.4.5 Internal Reference Clock ................................................................................................149
11.4.6 Optional External Reference Clock ................................................................................149
11.4.7 Fixed Frequency Clock ...................................................................................................149
Chapter 12
Modulo Timer (S08MTIMV1)
12.1 Introduction ...................................................................................................................................151
12.1.1 MTIM/TPM Configuration Information .........................................................................151
12.1.2 Features ...........................................................................................................................153
12.1.3 Modes of Operation ........................................................................................................153
12.1.4 Block Diagram ................................................................................................................154
12.2 External Signal Description ..........................................................................................................154
12.3 Register Definition ........................................................................................................................154
12.3.1 MTIM1 Status and Control Register (MTIM1SC) .........................................................156
12.3.2 MTIM1 Clock Configuration Register (MTIM1CLK) ...................................................157
12.3.3 MTIM1 Counter Register (MTIM1CNT) .......................................................................158
12.3.4 MTIM1 Modulo Register (MTIM1MOD) ......................................................................158
12.4 Functional Description ..................................................................................................................159
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12.4.1 MTIM Operation Example .............................................................................................160
Chapter 13
Timer/Pulse-Width Modulator (S08TPMV2)
13.1 Introduction ...................................................................................................................................161
13.1.1 ACMP/TPM Configuration Information ........................................................................161
13.1.2 MTIM/TPM Configuration Information .........................................................................161
13.1.3 Features ...........................................................................................................................163
13.1.4 Block Diagram ................................................................................................................163
13.2 External Signal Description ..........................................................................................................165
13.2.1 External TPM Clock Sources .........................................................................................165
13.2.2 TPMxCHn — TPMx Channel n I/O Pins .......................................................................165
13.3 Register Definition ........................................................................................................................165
13.3.1 Timer Status and Control Register (TPMxSC) ...............................................................166
13.3.2 Timer Counter Registers (TPMxCNTH:TPMxCNTL) ...................................................167
13.3.3 Timer Counter Modulo Registers (TPMxMODH:TPMxMODL) ..................................168
13.3.4 Timer Channel n Status and Control Register (TPMxCnSC) .........................................169
13.3.5 Timer Channel Value Registers (TPMxCnVH:TPMxCnVL) .........................................170
13.4 Functional Description ..................................................................................................................171
13.4.1 Counter ............................................................................................................................171
13.4.2 Channel Mode Selection .................................................................................................172
13.4.3 Center-Aligned PWM Mode ...........................................................................................174
13.5 TPM Interrupts ..............................................................................................................................175
13.5.1 Clearing Timer Interrupt Flags .......................................................................................175
13.5.2 Timer Overflow Interrupt Description ............................................................................175
13.5.3 Channel Event Interrupt Description ..............................................................................176
13.5.4 PWM End-of-Duty-Cycle Events ...................................................................................176
Chapter 14
Development Support
14.1 Introduction ...................................................................................................................................177
14.1.1 Module Configuration .....................................................................................................177
14.1.2 Features ...........................................................................................................................178
14.2 Background Debug Controller (BDC) ..........................................................................................178
14.2.1 BKGD Pin Description ...................................................................................................179
14.2.2 Communication Details ..................................................................................................180
14.2.3 BDC Commands .............................................................................................................182
14.2.4 BDC Hardware Breakpoint .............................................................................................185
14.3 On-Chip Debug System (DBG) ....................................................................................................186
14.3.1 Comparators A and B .....................................................................................................186
14.3.2 Bus Capture Information and FIFO Operation ...............................................................186
14.3.3 Change-of-Flow Information ..........................................................................................187
14.3.4 Tag vs. Force Breakpoints and Triggers .........................................................................187
14.3.5 Trigger Modes .................................................................................................................188
14.3.6 Hardware Breakpoints ....................................................................................................190
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14.4 Register Definition ........................................................................................................................190
14.4.1 BDC Registers and Control Bits .....................................................................................190
14.4.2 System Background Debug Force Reset Register (SBDFR) ..........................................192
14.4.3 DBG Registers and Control Bits .....................................................................................193
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Chapter 1
Device Overview
1.1
Introduction
The MC9S08QA4 series are members of the low-cost, high-performance HCS08 family of 8-bit
microcontroller units (MCUs). All MCUs in the family use the enhanced HCS08 core and are available
with a variety of modules, memory sizes, memory types, and package types. Refer to Table 1-1 for features
associated with each device in this series.
1.1.1
Devices in the MC9S08QA4 Series
Table 1-1 summarizes the features available in the MC9S08QA4 series of MCUs.
Table 1-1. Devices in the MC9S08QA4 Series
Feature
Device
MC9S08QA4
MC9S08QA2
Package
8-Pin
8-Pin
Flash
4K
2K
RAM
256
160
ICS
yes
ACMP
yes
ADC
4-ch
DBG
yes
IRQ
yes
KBI
4-pin
MTIM
yes
TPM
1-ch
I/O pins
4 I/O
1 output only
1 input only
Package
Types
8 DFN
8 SOIC
8 PDIP
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Chapter 1 Device Overview
1.1.2
MCU Block Diagram
BKGD/MS
IRQ
HCS08 CORE
DEBUG MODULE (DBG)
BDC
CPU
HCS08 SYSTEM CONTROL
TCLK
PTA4/ACMPO/BKGD/MS
COP
IRQ
LVD
USER FLASH
(MC9S08QA4 = 4096 BYTES)
(MC9S08QA2 = 2048 BYTES)
USER RAM
(MC9S08QA4 = 256 BYTES)
(MC9S08QA2 = 160BYTES)
PORT A
RESETS AND INTERRUPTS
MODES OF OPERATION
POWER MANAGEMENT
RTI
PTA5//IRQ/TCLK/RESET
8-BIT MODULO TIMER
MODULE (MTIM)
PTA3/KBIP3/ADP3
PTA2/KBIP2/ADP2
4
8-BIT KEYBOARD
INTERRUPT MODULE (KBI)
ANALOG COMPARATOR
(ACMP)
ACMPO
ACMP–
ACMP+
PTA1/KBIP1/ADP1/ACMP–
PTA0/KBIP0/TPMCH0/ADP0/ACMP+
4
10-BIT
ANALOG-TO-DIGITAL
CONVERTER (ADC)
16-BIT TIMER/PWM
MODULE (TPM)
TPMCH0
16 MHz INTERNAL CLOCK
SOURCE (ICS)
VSS
VDD
VOLTAGE REGULATOR
VDDA
VSSA
VREFH
VREFL
NOTES:
1 Port pins are software configurable with pullup device if input port.
2 Port pins are software configurable for output drive strength.
3 Port pins are software configurable for output slew rate control.
4 IRQ contains a software configurable (IRQPDD) pullup device if PTA5 enabled as IRQ pin function (IRQPE = 1).
5 RESET contains integrated pullup device if PTA5 enabled as reset pin function (RSTPE = 1).
6
PTA4 contains integrated pullup device if BKGD enabled (BKGDPE = 1).
7 When pin functions as KBI (KBIPEn = 1) and associated pin is configured to enable the pullup device, KBEDGn can
be used to reconfigure the pullup as a pulldown device.
Figure 1-1. MC9S08QA4 Series Block Diagram
Table 1-2 provides the functional versions of the on-chip modules.
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Chapter 1 Device Overview
Table 1-2. Versions of On-Chip Modules
Module
1.2
Version
Analog Comparator
(ACMP)
2
Analog-to-Digital Converter
(ADC)
1
Central Processing Unit
(CPU)
2
Internal Clock Source
(ICS)
1
Keyboard Interrupt
(KBI)
2
Modulo Timer
(MTIM)
1
Timer Pulse-Width Modulator
(TPM)
2
Debug Module
(DBG)
2
System Clock Distribution
Figure 1-2 shows a simplified clock connection diagram. Some modules in the MCU have selectable clock
inputs as shown. The clock inputs to the modules indicate which clock(s) are used to drive the module
function. All memory mapped registers associated with the modules are clocked with BUSCLK.
TCLK
SYSTEM
CONTROL
LOGIC
TPM
MTIM
ICSFFE
ICSFFCLK
ICS
ICSOUT
ICSLCLK
1
÷2
FIXED FREQ CLOCK (XCLK)
÷2
1 kHz
BUSCLK
COP
BDC
CPU
ADC
FLASH
RTI
1
ICSLCLK is the alternate BDC clock source for the MC9S08QA4 series.
ADC has min and max frequency requirements. See the ADC chapter and MC9S08QA4 Series Data Sheet.
3 Flash has frequency requirements for program and erase operation. See MC9S08QA4 Series Data Sheet.
2
Figure 1-2. System Clock Distribution Diagram
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Chapter 1 Device Overview
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Chapter 2
External Signal Description
This chapter describes signals that connect to package pins. It includes pinout diagrams, table of signal
properties, and detailed discussions of signals.
2.1
Device Pin Assignment
Figure 2-1 shows the pin assignments for the available packages. Table 1-1 lists package types available
for each device in the series.
PTA5/IRQ/TCLK/RESET
1
8
PTA0/KBIP0/TPMCH0/ADP0/ACMP+
PTA4/ACMPO/BKGD/MS
2
7
PTA1/KBIP1/ADP1/ACMP–
VDD
3
6
PTA2/KBIP2/ADP2
VSS
4
5
PTA3/KBIP3/ADP3
8-pin PDIP/SOIC
PTA5/IRQ/TCLK/RESET 1
8 PTA0/KBIP0/TPMCH0/ADP0/ACMP+
PTA4/ACMPO/BKGD/MS 2
VDD
7 PTA1/KBIP1/ADP1/ACMP–
3
6 PTA2/KBIP2/ADP2
VSS 4
5 PTA3/KBIP3/ADP3
8-pin DFN
Figure 2-1. 8-Pin Packages
2.2
Recommended System Connections
Figure 2-2 shows pin connections that are common to almost all MC9S08QA4 series application systems.
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Chapter 2 External Signal Description
MC9S08QA4
VDD
SYSTEM
POWER
+
3V
CBLK
CBY
+
10 μF
PTA0/KBIP0/TPMCH0/ADP0/ACMP+
VDD
PTA1/KBIP1/ADP1/ACMP–
PORT
A
0.1 μF
VSS
PTA2/KBIP2/ADP2
PTA3/KBIP3/ADP3
PTA4/ACMPO/BKGD/MS
PTA5/IRQ/TCLK/RESET
BACKGROUND HEADER
BKGD
VDD
VDD
ASYNCHRONOUS
4.7 kΩ–10 kΩ
INTERRUPT
INPUT
RESET/IRQ
0.1 μF
OPTIONAL
MANUAL
RESET
NOTES:
1. The RESET pin can only be used to reset into user mode; you cannot enter BDM using the RESET pin.
BDM can be entered by holding MS low during POR or writing a 1 to BDFR in SBDFR with MS low after
issuing the BDM command.
2. IRQ feature has optional internal pullup device.
3. RC filter on RESET/IRQ pin recommended for noisy environments.
Figure 2-2. Basic System Connections
2.2.1
Power
VDD and VSS are the primary power supply pins for the MCU. This voltage source supplies power to all
I/O buffer circuitry, ACMP and ADC modules, and to an internal voltage regulator. The internal voltage
regulator provides a regulated lower-voltage source to the CPU and other internal circuitry of the MCU.
Typically, application systems have two separate capacitors across the power pins: a bulk electrolytic
capacitor, such as a 10-μF tantalum capacitor, to provide bulk charge storage for the overall system, and a
bypass capacitor, such as a 0.1-μF ceramic capacitor, located as near to the MCU power pins as practical
to suppress high-frequency noise.
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Chapter 2 External Signal Description
2.2.2
Reset (Input Only)
After a power-on reset (POR), the PTA5/IRQ/TCLK/RESET pin defaults to a general-purpose input port
pin, PTA5. Setting RSTPE in SOPT1 configures the pin to be the RESET input pin. After configured as
RESET, the pin will remain RESET until the next POR. The RESET pin can be used to reset the MCU
from an external source when the pin is driven low. When enabled as the RESET pin (RSTPE = 1), an
internal pullup device is automatically enabled.
NOTE
This pin does not contain a clamp diode to VDD and must not be driven
above VDD.
The voltage measured on the internally pulled up RESET pin will not be
pulled to VDD. The internal gates connected to this pin are pulled to VDD.
The RESET pullup must not be used to pull up components external to the
MCU.
NOTE
In EMC-sensitive applications, an external RC filter is recommended on the
RESET pin, if enabled. See Figure 2-2 for an example.
2.2.3
Background / Mode Select (BKGD/MS)
During a power-on-reset (POR) or background debug force reset (see 5.8.3, “System Background Debug
Force Reset Register (SBDFR),” for more information), the PTA4/ACMPO/BKGD/MS pin functions as a
mode select pin. Immediately after any reset, the pin functions as the background pin and can be used for
background debug communication. When enabled as the BKGD/MS pin (BKGDPE = 1), an internal
pullup device is automatically enabled.
The background debug communication function is enabled when BKGDPE in SOPT1 is set. BKGDPE is
set following any reset of the MCU and must be cleared to use the PTA4/ACMPO/BKGD/MS pin’s
alternative pin functions.
If nothing is connected to this pin, the MCU will enter normal operating mode at the rising edge of the
internal reset after a POR or force BDC reset. If a debug system is connected to the 6-pin standard
background debug header, it can hold BKGD/MS low during a POR or immediately after issuing a
background debug force reset, which will force the MCU to active background mode.
The BKGD pin is used primarily for background debug controller (BDC) communications using a custom
protocol that uses 16 clock cycles of the target MCU’s BDC clock per bit time. The target MCU’s BDC
clock could be as fast as the maximum bus clock rate, so there must never be any significant capacitance
connected to the BKGD/MS pin that could interfere with background serial communications.
Although the BKGD pin is a pseudo open-drain pin, the background debug communication protocol
provides brief, actively driven, high speedup pulses to ensure fast rise times. Small capacitances from
cables and the absolute value of the internal pullup device play almost no role in determining rise and fall
times on the BKGD pin.
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Chapter 2 External Signal Description
2.2.4
General-Purpose I/O and Peripheral Ports
Members of the MC9S08QA4 series of MCUs support up to four general-purpose I/O pins, one input-only
pin, and one output-only pin, which are shared with on-chip peripheral functions (timers, serial I/O, ADC,
keyboard interrupts, etc.). On each MC9S08QA4 series device, there is one input-only and one output-only
port pin.
When a port pin is configured as a general-purpose output or a peripheral uses the port pin as an output,
software can select one of two drive strengths and enable or disable slew rate control. When a port pin is
configured as a general-purpose input or a peripheral uses the port pin as an input, software can enable a
pullup device.
For information about controlling these pins as general-purpose I/O pins, see Chapter 6, “Parallel
Input/Output Control.” For information about how and when on-chip peripheral systems use these pins,
see the appropriate chapter referenced in Table 2-2.
Immediately after reset, all pins that are not output-only are configured as high-impedance
general-purpose inputs with internal pullup devices disabled. After reset, the output-only port function is
not enabled but is configured for low output drive strength with slew rate control enabled. The PTA4 pin
defaults to BKGD/MS on any reset.
NOTE
To avoid extra current drain from floating input pins, the reset initialization
routine in the application program must either enable on-chip pullup devices
or change the direction of unused pins to outputs so the pins do not float.
2.2.4.1
Pin Control Registers
To select drive strength or to enable slew rate control or pullup devices, the user writes to the appropriate
pin control register located in the high page register block of the memory map. The pin control registers
operate independently of the parallel I/O registers and allow control of a port on an individual pin basis.
2.2.4.1.1
Internal Pullup Enable
An internal pullup device can be enabled for each port pin by setting the corresponding bit in one of the
pullup enable registers (PTxPEn). The pullup device is disabled if the pin is configured as an output by the
parallel I/O control logic or by any shared peripheral function, regardless of the state of the corresponding
pullup enable register bit. The pullup device is also disabled if the pin is controlled by an analog function.
The KBI module, when enabled for rising edge detection, causes an enabled internal pull device to be
configured as a pulldown.
2.2.4.2
Output Slew Rate Control
Slew rate control can be enabled for each port pin by setting the corresponding bit in one of the slew rate
control registers (PTxSEn). When enabled, slew control limits the rate at which an output can transition in
order to reduce EMC emissions. Slew rate control has no effect on pins that are configured as inputs.
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Chapter 2 External Signal Description
2.2.4.3
Output Drive Strength Select
An output pin can be selected to have high output drive strength by setting the corresponding bit in one of
the drive strength select registers (PTxDSn). When high drive is selected, a pin is capable of sourcing and
sinking greater current. Even though every I/O pin can be selected as high drive, the user must ensure that
the total current source and sink limits for the chip are not exceeded. Drive strength selection is intended
to affect the DC behavior of I/O pins. However, the AC behavior is also affected. High drive allows a pin
to drive a greater load with the same switching speed as a low-drive-enabled pin into a smaller load.
Because of this, the EMC emissions may be affected if pins are enabled as high drive.
Table 2-1. Pin Sharing Priority
Priority
PIN
8-pin
Lowest
Port Pin
1
PTA51
2
PTA4
Highest
Alt 1
IRQ
Alt 2
Alt 3
TCLK
ACMPO
Alt 4
RESET
BKGD
MS
3
VDD
4
VSS
5
PTA3
KBIP3
ADP3
6
PTA2
KBIP2
ADP2
7
PTA1
KBIP1
8
PTA0
KBIP0
TPMCH0
ADP12
ACMP–2
ADP02
ACMP+2
1
Pin does not contain a clamp diode to VDD and must not be driven
above VDD. The voltage measured on the internally pulled-up RESET
pin will not be pulled to VDD. The internal gates connected to this pin
are pulled to VDD.
2 If ACMP and ADC are both enabled, both will have access to the pin.
Table 2-2. Pin Function Reference
Signal Function
Example(s)
Reference
Port Pins
PTAx
Chapter 6, “Parallel Input/Output Control”
Analog comparator
ACMPO, ACMP–, ACMP+
Chapter 9, “Analog Comparator (S08ACMPV2)”
Keyboard interrupts
KBIPx
Chapter 8, “Keyboard Interrupt (S08KBIV2)”
Timer/PWM
TCLK, TPMCHx
Chapter 13, “Timer/Pulse-Width Modulator (S08TPMV2)”
Analog-to-digital
ADPx
Chapter 10, “Analog-to-Digital Converter (S08ADC10V1)”
Power/core
BKGD/MS, VDD, VSS
Chapter 2, “External Signal Description”
Reset and interrupts
RESET, IRQ
Chapter 5, “Resets, Interrupts, and General System Control”
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Chapter 2 External Signal Description
NOTE
When an alternative function is first enabled, it is possible to get a spurious
edge to the module. User software must clear out any associated flags before
interrupts are enabled. Table 2-1 shows the priority if multiple modules are
enabled. The highest priority module will have control over the pin.
Selecting a higher priority pin function with a lower priority function
already enabled can cause spurious edges to the lower priority module. It is
recommended that all modules that share a pin be disabled before enabling
anther module.
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Freescale Semiconductor
Chapter 3
Modes of Operation
3.1
Introduction
The operating modes of the MC9S08QA4 series are described in this chapter. Entry into each mode, exit
from each mode, and functionality while in each mode are described.
3.2
•
•
•
3.3
Features
Active background mode for code development
Wait mode:
— CPU halts operation to conserve power
— System clocks continue to run
— Full voltage regulation is maintained
Stop modes: CPU and bus clocks stopped
— Stop1: Full powerdown of internal circuits for maximum power savings
— Stop2: Partial powerdown of internal circuits; RAM contents retained
— Stop3: All internal circuits powered for fast recovery; RAM and register contents are retained
Run Mode
Run is the normal operating mode for the MC9S08QA4 series. This mode is selected upon the MCU
exiting reset if the BKGD/MS pin is high. In this mode, the CPU executes code from internal memory with
execution beginning at the address fetched from memory at 0xFFFE:0xFFFF after reset.
3.4
Active Background Mode
The active background mode functions are managed through the background debug controller (BDC) in
the HCS08 core. The BDC, together with the on-chip debug module (DBG), provides the means for
analyzing MCU operation during software development.
Active background mode is entered in any of five ways:
• When the BKGD/MS pin is low during POR or immediately after issuing a background debug
force reset (see 5.8.3, “System Background Debug Force Reset Register (SBDFR)”)
• When a BACKGROUND command is received through the BKGD pin
• When a BGND instruction is executed
• When encountering a BDC breakpoint
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Chapter 3 Modes of Operation
•
When encountering a DBG breakpoint
After entering active background mode, the CPU is held in a suspended state waiting for serial background
commands rather than executing instructions from the user application program.
Background commands are of two types:
• Non-intrusive commands, defined as commands that can be issued while the user program is
running. Non-intrusive commands can be issued through the BKGD pin while the MCU is in run
mode; non-intrusive commands can also be executed when the MCU is in the active background
mode. Non-intrusive commands include:
— Memory access commands
— Memory-access-with-status commands
— BDC register access commands
— The BACKGROUND command
• Active background commands, which can only be executed while the MCU is in active background
mode. Active background commands include commands to:
— Read or write CPU registers
— Trace one user program instruction at a time
— Leave active background mode to return to the user application program (GO)
The active background mode is used to program a bootloader or user application program into the flash
program memory before the MCU is operated in run mode for the first time. When the MC9S08QA4 series
MCUs are shipped from the Freescale factory, the flash program memory is erased by default unless
specifically noted, so there is no program that could be executed in run mode until the flash memory is
initially programmed. The active background mode can also be used to erase and reprogram the flash
memory after it has been previously programmed.
For additional information about the active background mode, refer to Chapter 14, “Development
Support.”
3.5
Wait Mode
Wait mode is entered by executing a WAIT instruction. Upon execution of the WAIT instruction, the CPU
enters a low-power state in which it is not clocked. The I bit in the condition code register (CCR) is cleared
when the CPU enters wait mode, enabling interrupts. When an interrupt request occurs, the CPU exits wait
mode and resumes processing, beginning with the stacking operations leading to the interrupt service
routine.
While the MCU is in wait mode, background debug commands can be used on restrictions.
Only the BACKGROUND command and memory-access-with-status commands are available while the
MCU is in wait mode. The memory-access-with-status commands do not allow memory access, but they
report an error indicating that the MCU is in stop or wait mode. The BACKGROUND command can be
used to wake the MCU from wait mode and enter active background mode.
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Chapter 3 Modes of Operation
3.6
Stop Modes
One of three stop modes is entered upon execution of a STOP instruction when STOPE in SOPT1 is set.
In any stop mode, the bus and CPU clocks are halted. The ICS module can be configured to leave the
reference clocks running. See Chapter 11, “Internal Clock Source (S08ICSV1),” for more information.
Table 3-1 shows all of the control bits that affect stop mode selection and the mode selection under various
conditions. The selected mode is entered following the execution of a STOP instruction.
Table 3-1. Stop Mode Selection
STOPE
ENBDM 1
0
x
1
LVDE
LVDSE
PDC
PPDC
Stop Mode
x
x
x
Stop modes disabled; illegal opcode reset if STOP
instruction executed
1
x
x
x
Stop3 with BDM enabled 2
1
0
Both bits must be 1
x
x
Stop3 with voltage regulator active
1
0
Either bit a 0
0
x
Stop3
1
0
Either bit a 0
1
1
Stop2
1
0
Either bit a 0
1
0
Stop1
1
ENBDM is located in the BDCSCR which is only accessible through BDC commands; see Section 14.4.1.1, “BDC
Status and Control Register (BDCSCR)”.
2 When in Stop3 mode with BDM enabled, the S
IDD will be near RIDD levels because internal clocks are enabled
NOTE
The PORT register must be initialized as 0xFF in order to ensure that the low
power specifications will be met. User software must write 0xff to location
0x03.
3.6.1
Stop3 Mode
Stop3 mode is entered by executing a STOP instruction under the conditions shown in Table 3-1. The
states of all of the internal registers and logic, RAM contents, and I/O pin states are maintained.
Stop3 can be exited by asserting RESET, or by an interrupt from one of the following sources: the real-time
interrupt (RTI), LVD, ADC, IRQ, or the KBI.
If stop3 is exited by means of the RESET pin, then the MCU is reset and operation will resume after taking
the reset vector. Exit by means of one of the internal interrupt sources will result in the MCU taking the
appropriate interrupt vector.
NOTE
The PORT register must be initialized as 0xFF in order to ensure that the low
power specifications will be met. User software must write 0xFF to location
0x03.
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Chapter 3 Modes of Operation
3.6.1.1
LVD Enabled in Stop Mode
The LVD system is capable of generating either an interrupt or a reset when the supply voltage drops below
the LVD voltage. If the LVD is enabled in stop (LVDE and LVDSE bits in SPMSC1 both set) at the time
the CPU executes a STOP instruction, then the voltage regulator remains active during stop mode.
For the ADC to operate, the LVD must remain enabled when entering stop3.
3.6.1.2
Active BDM Enabled in Stop Mode
Entry into the active background mode from run mode is enabled if ENBDM in BDCSCR is set. This
register is described in Chapter 14, “Development Support.” If ENBDM is set when the CPU executes a
STOP instruction, the system clocks to the background debug logic remain active when the MCU enters
stop mode. Because of this, background debug communication remains possible. In addition, the voltage
regulator does not enter its low-power standby state but maintains full internal regulation.
Most background commands are not available in stop mode. The memory-access-with-status commands
do not allow memory access, but they report an error indicating that the MCU is in either stop or wait
mode. The BACKGROUND command can be used to wake the MCU from stop and enter active
background mode if the ENBDM bit is set. After entering background debug mode, all background
commands are available.
3.6.2
Stop2 Mode
Stop2 mode is entered by executing a STOP instruction under the conditions shown in Table 3-1. Most of
the internal circuitry of the MCU is powered off in stop2 as in stop1, with the exception of the RAM. Upon
entering stop2, all I/O pin control signals are latched so that the pins retain their states during stop2.
Exit from stop2 is performed by asserting the wake-up pin (PTA5) on the MCU.
NOTE
PTA5/IRQ/TCLK/RESET always functions as an active-low wakeup input
when the MCU is in stop2, regardless of how the pin is configured before
entering stop2. The pullup is not automatically enabled. To use the internal
pullup, set the PTAPE5 bit in the PTAPE register.
NOTE
The PORT register must be initialized as 0xFF in order to ensure that the low
power specifications will be met. User software must write 0xFF to location
0x03.
In addition, the real-time interrupt (RTI) can wake the MCU from stop2, if enabled.
Upon wake-up from stop2 mode, the MCU starts up as from a power-on reset (POR):
• All module control and status registers are reset
• The LVD reset function is enabled and the MCU remains in the reset state if VDD is below the LVD
trip point (low trip point selected due to POR)
• The CPU takes the reset vector
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Chapter 3 Modes of Operation
In addition to the above, upon waking up from stop2, the PPDF bit in SPMSC2 is set. This flag is used to
direct user code to go to a stop2 recovery routine. PPDF remains set and the I/O pin states remain latched
until a 1 is written to PPDACK in SPMSC2.
To maintain I/O states for pins that were configured as general-purpose I/O before entering stop2, the user
must restore the contents of the I/O port registers, which have been saved in RAM, to the port registers
before writing to the PPDACK bit. If the port registers are not restored from RAM before writing to
PPDACK, then the pins will switch to their reset states when PPDACK is written.
For pins that were configured as peripheral I/O, the user must reconfigure the peripheral module that
interfaces to the pin before writing to the PPDACK bit. If the peripheral module is not enabled before
writing to PPDACK, the pins will be controlled by their associated port control registers when the I/O
latches are opened.
3.6.3
Stop1 Mode
Stop1 mode is entered by executing a STOP instruction under the conditions shown in Table 3-1. Most of
the internal circuitry of the MCU is powered off in stop1, providing the lowest possible standby current.
Upon entering stop1, all I/O pins automatically transition to their default reset states.
Exit from stop1 is performed by asserting the wake-up pin (PTA5) on the MCU.
NOTE
PTA5/IRQ/TCLK/RESET always functions as an active-low wakeup input
when the MCU is in stop1, regardless of how the pin is configured before
entering stop1. The pullup is not automatically enabled. To use the internal
pullup, set the PTAPE5 bit in the PTAPE register.
NOTE
The PORT register must be initialized as 0xFF in order to ensure that the low
power specifications will be met. User software must write 0xFF to location
0x03.
In addition, the real-time interrupt (RTI) can wake the MCU from stop1 if enabled.
Upon wake-up from stop1 mode, the MCU starts up as from a power-on reset (POR):
• All module control and status registers are reset
• The LVD reset function is enabled and the MCU remains in the reset state if VDD is below the LVD
trip point (low trip point selected due to POR)
• The CPU takes the reset vector
In addition to the above, upon waking up from stop1, the PDF bit in SPMSC2 is set. This flag is used to
direct user code to go to a stop1 recovery routine. PDF remains set until a 1 is written to PPDACK in
SPMSC2.
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Chapter 3 Modes of Operation
3.6.4
On-Chip Peripheral Modules in Stop Modes
When the MCU enters any stop mode, system clocks to the internal peripheral modules are stopped. Even
in the exception case (ENBDM = 1), where clocks to the background debug logic continue to operate,
clocks to the peripheral systems are halted to reduce power consumption. Refer to Section 3.6.3, “Stop1
Mode,” Section 3.6.2, “Stop2 Mode,” and Section 3.6.1, “Stop3 Mode,” for specific information on
system behavior in stop modes.
Table 3-2. Stop Mode Behavior
Mode
Peripheral
Stop1
Stop2
Stop3
CPU
Off
Off
Standby
RAM
Off
Standby
Standby
Flash
Off
Off
Standby
Parallel Port Registers
Off
Off
Standby
ADC
Off
Off
Optionally On1
ACMP
Off
Off
Standby
ICS
Off
Off
Optionally On2
MTIM
Off
Off
Standby
TPM
Off
Off
Standby
Voltage Regulator
Off
Standby
Standby
I/O Pins
Hi-Z
States Held
States Held
1
2
Requires the asynchronous ADC clock and LVD to be enabled, else in standby.
IRCLKEN and IREFSTEN set in ICSC1, else in standby.
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Chapter 4
Memory Map and Register Definition
4.1
MC9S08QA4 Series Memory Map
As shown in Figure 4-1, on-chip memory in the MC9S08QA4 series of MCUs consists of RAM, flash
program memory for nonvolatile data storage, and I/O and control/status registers. The registers are
divided into these groups:
• Direct-page registers (0x0000 through 0x005F)
• High-page registers (0x1800 through 0x184F)
• Nonvolatile registers (0xFFB0 through 0xFFBF)
0x0000
0x005F
0x0060
DIRECT PAGE REGISTERS
RAM
256 BYTES
0x015F
0x0160
0x17FF
0x1800
UNIMPLEMENTED
0x0000
0x005F
0x0060
0x00FF
0x0100
0x025F
0x0260
0x17FF
0x1800
RAM
160 BYTES
RESERVED
UNIMPLEMENTED
5536 BYTES
HIGH PAGE REGISTERS
HIGH PAGE REGISTERS
0x184F
0x1850
0x184F
0x1850
UNIMPLEMENTED
UNIMPLEMENTED
51,120 BYTES
51,120 BYTES
0xDFFF
0xE000
0xDFFF
0xE000
RESERVED
0xEFFF
0xF000
DIRECT PAGE REGISTERS
RESERVED
4096 BYTES
FLASH
4096 BYTES
4096 BYTES
0xF7FF
0xF800
0xFFFF
0xFFFF
MC9S08QA4
FLASH
2048 BYTES
MC9S08QA2
Figure 4-1. MC9S08QA4 Series Memory Map
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Chapter 4 Memory Map and Register Definition
4.2
Reset and Interrupt Vector Assignments
Table 4-1 shows address assignments for reset and interrupt vectors. The vector names shown in this table
are the labels used in the Freescale Semiconductor-provided equate file for the MC9S08QA4 series.
Table 4-1. Reset and Interrupt Vectors
Address
(High:Low)
Vector
Vector Name
0xFFC0:FFC1
Unused Vector Space
(available for user program)
0xFFCE:FFCF
0xFFD0:FFD1
RTI
Vrti
0xFFD2:FFD3
Reserved
—
0xFFD4:FFD5
Reserved
—
0xFFD6:FFD7
ACMP
Vacmp
0xFFD8:FFD9
ADC Conversion
Vadc
0xFFDA:FFDB
KBI Interrupt
Vkeyboard
0xFFDC:FFDD
Reserved
Viic
0xFFDE:FFDF
Reserved
Vscitx
0xFFE0:FFE1
Reserved
Vscirx
0xFFE2:FFE3
Reserved
Vscierr
0xFFE4:FFE5
Reserved
Vspi
0xFFE6:FFE7
MTIM Overflow
Vmtim
0xFFE8:FFE9
Reserved
—
0xFFEA:FFEB
Reserved
—
0xFFEC:FFED
Reserved
—
0xFFEE:FFEF
Reserved
—
0xFFF0:FFF1
TPM Overflow
Vtpmovf
0xFFF2:FFF3
Reserved
—
0xFFF4:FFF5
TPM Channel 0
Vtpmch0
0xFFF6:FFF7
Reserved
—
0xFFF8:FFF9
Low Voltage Detect
Vlvd
0xFFFA:FFFB
IRQ
Virq
0xFFFC:FFFD
SWI
Vswi
0xFFFE:FFFF
Reset
Vreset
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Chapter 4 Memory Map and Register Definition
4.3
Register Addresses and Bit Assignments
The registers in the MC9S08QA4 series are divided into these groups:
• Direct-page registers are located in the first 96 locations in the memory map; these are accessible
with efficient direct addressing mode instructions.
• High-page registers are used much less often, so they are located from 0x1800 and above in the
memory map. This leaves more room in the direct page for more frequently used registers and
RAM.
• The nonvolatile register area consists of a block of 16 locations in flash memory at
0xFFB0–0xFFBF. Nonvolatile register locations include:
— NVPROT and NVOPT, which are loaded into working registers at reset.
— An 8-byte backdoor comparison key that optionally allows a user to gain controlled access to
secure memory.
Because the nonvolatile register locations are flash memory, they must be erased and programmed
like other flash memory locations.
Direct-page registers can be accessed with efficient direct addressing mode instructions. Bit manipulation
instructions can be used to access any bit in any direct-page register. Table 4-2 is a summary of all
user-accessible direct-page registers and control bits.
The direct page registers in Table 4-2 can use the more efficient direct addressing mode that requires only
the lower byte of the address. Because of this, the lower byte of the address in column one is shown in bold
text. In Table 4-3 and Table 4-4, the whole address in column one is shown in bold. In Table 4-2, Table 4-3,
and Table 4-4, the register names in column two are shown in bold to set them apart from the bit names to
the right. Cells that are not associated with named bits are shaded. A shaded cell with a 0 indicates this
unused bit always reads as a 0. Shaded cells with dashes indicate unused or reserved bit locations that could
read as 1s or 0s.
Table 4-2. Direct-Page Register Summary
Address
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
0x0000
PTAD
0
0
PTAD5
PTAD4
PTAD3
PTAD2
PTAD1
PTAD0
0x0001
PTADD
0
0
PTADD5
PTADD4
PTADD3
PTADD2
PTADD1
PTADD0
—
—
—
—
—
—
—
—
0x0002
Reserved
0x0003
PORT
0x0004–
0x000B
Reserved
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
0x000C
KBISC
0
0
0
0
KBF
KBACK
KBIE
KBIMOD
0x000D
KBIPE
0
0
0
0
KBIPE3
KBIPE2
KBIPE1
KBIPE0
0x000E
KBIES
0
0
0
0
KBEDG3
KBEDG2
KBEDG1
KBEDG0
0x000F
IRQSC
0
IRQPDD
0
IRQPE
IRQF
IRQACK
IRQIE
IRQMOD
0x0010
ADCSC1
COCO
AIEN
ADCO
0x0011
ADCSC2
ADACT
ADTRG
ACFE
ACFGT
—
—
—
—
0x0012
ADCRH
0
0
0
0
0
0
ADR9
ADR8
0x0013
ADCRL
ADR7
ADR6
ADR5
ADR4
ADR3
ADR2
ADR1
ADR0
PORT
ADCH
MC9S08QA4 MCU Series Reference Manual, Rev. 2
Freescale Semiconductor
35
Chapter 4 Memory Map and Register Definition
Table 4-2. Direct-Page Register Summary (continued)
Address
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
0x0014
ADCCVH
0
0
0
0
0
0
ADCV9
ADCV8
0x0015
ADCCVL
ADCV7
ADCV6
ADCV5
ADCV4
ADCV3
ADCV2
ADCV1
ADCV0
0x0016
ADCCFG
ADLPC
0x0017
APCTL1
0
0
0
0
ADPC3
ADPC2
ADPC1
ADPC0
0x0018
Reserved
0
0
0
0
0
0
0
0
0x0019
Reserved
0
0
0
0
0
0
0
0
0x001A
ADIV
ADLSMP
MODE
ADICLK
ACMPSC
ACME
ACBGS
ACF
ACIE
ACO
ACOPE
0x001B–
0x0037
Reserved
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
0x0038
ICSC1
CLKS
IREFS
IRCLKEN
IREFSTEN
0x0039
ICSC2
BDIV
EREFS
ERCLKEN EREFSTEN
0x003A
ICSTRM
0x003B
ICSSC
0x003C
RDIV
RANGE
HGO
LP
ACMOD
TRIM
0
0
0
0
MTIMSC
TOF
TOIE
TRST
TSTP
0x003D
MTIMCLK
0
0
0x003E
MTIMCNT
COUNT
0x003F
MTIMMOD
MOD
0x0040
TPMSC
TOF
TOIE
CPWMS
CLKSB
CLKSA
0x0041
TPMCNTH
Bit 15
14
13
12
11
OSCINIT
FTRIM
0
0
PS2
PS1
PS0
10
9
Bit 8
CLKST
0
0
CLKS
PS
0x0042
TPMCNTL
Bit 7
6
5
4
3
2
1
Bit 0
0x0043
TPMMODH
Bit 15
14
13
12
11
10
9
Bit 8
0x0044
TPMMODL
Bit 7
6
5
4
3
2
1
Bit 0
0x0045
TPMC0SC
CH0F
CH0IE
MS0B
MS0A
ELS0B
ELS0A
0
0
0x0046
TPMC0VH
Bit 15
14
13
12
11
10
9
Bit 8
0x0047
TPMC0VL
Bit 7
6
5
4
3
2
1
Bit 0
0x0048–
0x005F
Reserved
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
High-page registers, shown in Table 4-3, are accessed much less often than other I/O and control registers
so they have been located outside the direct addressable memory space, starting at 0x1800.
Table 4-3. High-Page Register Summary
Address
0x1800
Register Name
SRS
Bit 7
6
5
4
3
2
1
Bit 0
POR
PIN
COP
ILOP
ILAD
0
LVD
0
0x1801
SBDFR
0
0
0
0
0
0
0
BDFR
0x1802
SOPT1
COPE
COPT
STOPE
—
0
0
BKGDPE
RSTPE
0x1803
SOPT2
COPCLKS
0
0
0
0
0
0
ACIC
0x1804
Reserved
—
—
—
—
—
—
—
—
0x1805
Reserved
—
—
—
—
—
—
—
—
0x1806
SDIDH
—
—
—
—
ID11
ID10
ID9
ID8
0x1807
SDIDL
ID7
ID6
ID5
ID4
ID3
ID2
ID1
ID0
MC9S08QA4 MCU Series Reference Manual, Rev. 2
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Freescale Semiconductor
Chapter 4 Memory Map and Register Definition
Table 4-3. High-Page Register Summary (continued)
Bit 7
6
5
4
3
0x1808
Address
SRTISC
Register Name
RTIF
RTIACK
0
RTIE
0
2
1
Bit 0
0x1809
SPMSC1
LVDF
LVDACK
LVDIE
LVDRE
LVDSE
LVDE
0
BGBE
0x180A
SPMSC2
0
0
0
PDF
PPDF
PPDACK
PDC
PPDC
RTIS
0x180B
Reserved
—
—
—
—
—
—
—
—
0x180C
SPMSC3
LVWF
LVWACK
LVDV
LVWV
—
—
—
—
0x180D–
0x180F
Reserved
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
0x1810
DBGCAH
Bit 15
14
13
12
11
10
9
Bit 8
0x1811
DBGCAL
Bit 7
6
5
4
3
2
1
Bit 0
0x1812
DBGCBH
Bit 15
14
13
12
11
10
9
Bit 8
0x1813
DBGCBL
Bit 7
6
5
4
3
2
1
Bit 0
0x1814
DBGFH
Bit 15
14
13
12
11
10
9
Bit 8
0x1815
DBGFL
Bit 7
6
5
4
3
2
1
Bit 0
0x1816
DBGC
DBGEN
ARM
TAG
BRKEN
RWA
RWAEN
RWB
RWBEN
0x1817
DBGT
TRGSEL
BEGIN
0
0
TRG3
TRG2
TRG1
TRG0
0x1818
DBGS
AF
BF
ARMF
0
CNT3
CNT2
CNT1
CNT0
0x1819–
0x181F
Reserved
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
0x1820
FCDIV
DIVLD
PRDIV8
0x1821
FOPT
KEYEN
FNORED
0
0
0
0
SEC01
SEC00
0x1822
Reserved
—
—
—
—
—
—
—
—
0
0
KEYACC
0
0
0
0
DIV
0x1823
FCNFG
0x1824
FPROT
0x1825
FSTAT
0x1826
FCMD
0x1827–
0x183F
Reserved
—
—
—
—
—
—
0x1840
PTAPE
0
0
0x1841
PTASE
0
0x1842
PTADS
0x18430x1847
Reserved
FPS
FCBEF
FCCF
FPVIOL
0
FPDIS
FACCERR
0
FBLANK
0
0
—
—
—
—
—
—
—
—
—
—
PTAPE5
PTAPE4
PTAPE3
PTAPE2
PTAPE1
PTAPE0
0
PTASE5
PTASE4
PTASE3
PTASE2
PTASE1
PTASE0
0
0
PTADS5
PTADS4
PTADS3
PTADS2
PTADS1
PTADS0
—
—
—
—
—
—
—
—
FCMD
Nonvolatile flash registers, shown in Table 4-4, are located in the flash memory. These registers include
an 8-byte backdoor key that optionally can be used to gain access to secure memory resources. During
reset events, the contents of NVPROT and NVOPT in the nonvolatile register area of the flash memory
are transferred into corresponding FPROT and FOPT working registers in the high-page registers to
control security and block protection options.
MC9S08QA4 MCU Series Reference Manual, Rev. 2
Freescale Semiconductor
37
Chapter 4 Memory Map and Register Definition
Table 4-4. Nonvolatile Register Summary
Address
Register Name
0xFFAE
Reserved for
Storage of FTRIM
0xFFAF
Reserved for
Storage of ICSTRM
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
FTRIM
—
—
—
—
—
—
TRIM
0xFFB0 – NVBACKKEY
0xFFB7
0xFFB8 – Unused
0xFFBC
8-Byte Comparison Key
—
—
—
—
—
—
—
—
—
—
0xFFBD
NVPROT
FPS
FPDIS
0xFFBE
Unused
—
—
—
—
—
—
—
—
0xFFBF
NVOPT
KEYEN
FNORED
0
0
0
0
SEC01
SEC00
Provided the key enable (KEYEN) bit is 1, the 8-byte comparison key can be used to temporarily
disengage memory security. This key mechanism can be accessed only through user code running in secure
memory. (A security key cannot be entered directly through background debug commands.) This security
key can be disabled completely by programming the KEYEN bit to 0. If the security key is disabled, the
only way to disengage security is by mass erasing the flash if needed (normally through the background
debug interface) and verifying that flash is blank. To avoid returning to secure mode after the next reset,
program the security bits (SEC01:SEC00) to the unsecured state (1:0).
4.4
RAM
The MC9S08QA4 series includes static RAM. The locations in RAM below 0x0100 can be accessed using
the more efficient direct addressing mode, and any single bit in this area can be accessed with the bit
manipulation instructions (BCLR, BSET, BRCLR, and BRSET). Locating the most frequently accessed
program variables in this area of RAM is preferred.
The RAM retains data when the MCU is in low-power wait, stop2, or stop3 mode. At power-on or after
wakeup from stop1, the contents of RAM are uninitialized. RAM data is unaffected by any reset, provided
that the supply voltage does not drop below the minimum value for RAM retention (VRAM).
For compatibility with M68HC05 MCUs, the HCS08 resets the stack pointer to 0x00FF. In the
MC9S08QA4 series, it is usually best to reinitialize the stack pointer to the top of the RAM so the direct
page RAM can be used for frequently accessed RAM variables and bit-addressable program variables.
Include the following 2-instruction sequence in your reset initialization routine (where RamLast is equated
to the highest address of the RAM in the Freescale Semiconductor-provided equate file).
LDHX
TXS
#RamLast+1
;point one past RAM
;SP fADCK
xx
0
17 ADCK cycles
Subsequent continuous 10-bit;
fBUS > fADCK
xx
0
20 ADCK cycles
Subsequent continuous 8-bit;
fBUS > fADCK/11
xx
1
37 ADCK cycles
Subsequent continuous 10-bit;
fBUS > fADCK/11
xx
1
40 ADCK cycles
The maximum total conversion time is determined by the clock source chosen and the divide ratio selected.
The clock source is selectable by the ADICLK bits, and the divide ratio is specified by the ADIV bits. For
example, in 10-bit mode, with the bus clock selected as the input clock source, the input clock divide-by-1
ratio selected, and a bus frequency of 8 MHz, then the conversion time for a single conversion is:
Conversion time =
23 ADCK cyc
8 MHz/1
+
5 bus cyc
8 MHz
= 3.5 μs
Number of bus cycles = 3.5 μs x 8 MHz = 28 cycles
NOTE
The ADCK frequency must be between fADCK minimum and fADCK
maximum to meet ADC specifications.
MC9S08QA4 MCU Series Reference Manual, Rev. 2
Freescale Semiconductor
129
Analog-to-Digital Converter (S08ADC10V1)
10.4.5
Automatic Compare Function
The compare function can be configured to check for either an upper limit or lower limit. After the input
is sampled and converted, the result is added to the two’s complement of the compare value (ADCCVH
and ADCCVL). When comparing to an upper limit (ACFGT = 1), if the result is greater-than or equal-to
the compare value, COCO is set. When comparing to a lower limit (ACFGT = 0), if the result is less than
the compare value, COCO is set. The value generated by the addition of the conversion result and the two’s
complement of the compare value is transferred to ADCRH and ADCRL.
Upon completion of a conversion while the compare function is enabled, if the compare condition is not
true, COCO is not set and no data is transferred to the result registers. An ADC interrupt is generated upon
the setting of COCO if the ADC interrupt is enabled (AIEN = 1).
NOTE
The compare function can be used to monitor the voltage on a channel while
the MCU is in either wait or stop3 mode. The ADC interrupt will wake the
MCU when the compare condition is met.
10.4.6
MCU Wait Mode Operation
The WAIT instruction puts the MCU in a lower power-consumption standby mode from which recovery
is very fast because the clock sources remain active. If a conversion is in progress when the MCU enters
wait mode, it continues until completion. Conversions can be initiated while the MCU is in wait mode by
means of the hardware trigger or if continuous conversions are enabled.
The bus clock, bus clock divided by two, and ADACK are available as conversion clock sources while in
wait mode. The use of ALTCLK as the conversion clock source in wait is dependent on the definition of
ALTCLK for this MCU. Consult the module introduction for information on ALTCLK specific to this
MCU.
A conversion complete event sets the COCO and generates an ADC interrupt to wake the MCU from wait
mode if the ADC interrupt is enabled (AIEN = 1).
10.4.7
MCU Stop3 Mode Operation
The STOP instruction is used to put the MCU in a low power-consumption standby mode during which
most or all clock sources on the MCU are disabled.
10.4.7.1
Stop3 Mode With ADACK Disabled
If the asynchronous clock, ADACK, is not selected as the conversion clock, executing a STOP instruction
aborts the current conversion and places the ADC in its idle state. The contents of ADCRH and ADCRL
are unaffected by stop3 mode.After exiting from stop3 mode, a software or hardware trigger is required to
resume conversions.
MC9S08QA4 MCU Series Reference Manual, Rev. 2
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Analog-to-Digital Converter (S08ADC10V1)
10.4.7.2
Stop3 Mode With ADACK Enabled
If ADACK is selected as the conversion clock, the ADC continues operation during stop3 mode. For
guaranteed ADC operation, the MCU’s voltage regulator must remain active during stop3 mode. Consult
the module introduction for configuration information for this MCU.
If a conversion is in progress when the MCU enters stop3 mode, it continues until completion. Conversions
can be initiated while the MCU is in stop3 mode by means of the hardware trigger or if continuous
conversions are enabled.
A conversion complete event sets the COCO and generates an ADC interrupt to wake the MCU from stop3
mode if the ADC interrupt is enabled (AIEN = 1).
NOTE
It is possible for the ADC module to wake the system from low power stop
and cause the MCU to begin consuming run-level currents without
generating a system level interrupt. To prevent this scenario, software
should ensure that the data transfer blocking mechanism (discussed in
Section 10.4.4.2, “Completing Conversions) is cleared when entering stop3
and continuing ADC conversions.
10.4.8
MCU Stop1 and Stop2 Mode Operation
The ADC module is automatically disabled when the MCU enters either stop1 or stop2 mode. All module
registers contain their reset values following exit from stop1 or stop2. Therefore the module must be
re-enabled and re-configured following exit from stop1 or stop2.
10.5
Initialization Information
This section gives an example which provides some basic direction on how a user would initialize and
configure the ADC module. The user has the flexibility of choosing between configuring the module for
8-bit or 10-bit resolution, single or continuous conversion, and a polled or interrupt approach, among many
other options. Refer to Table 10-6, Table 10-7, and Table 10-8 for information used in this example.
NOTE
Hexadecimal values designated by a preceding 0x, binary values designated
by a preceding %, and decimal values have no preceding character.
10.5.1
10.5.1.1
ADC Module Initialization Example
Initialization Sequence
Before the ADC module can be used to complete conversions, an initialization procedure must be
performed. A typical sequence is as follows:
1. Update the configuration register (ADCCFG) to select the input clock source and the divide ratio
used to generate the internal clock, ADCK. This register is also used for selecting sample time and
low-power configuration.
MC9S08QA4 MCU Series Reference Manual, Rev. 2
Freescale Semiconductor
131
Analog-to-Digital Converter (S08ADC10V1)
2. Update status and control register 2 (ADCSC2) to select the conversion trigger (hardware or
software) and compare function options, if enabled.
3. Update status and control register 1 (ADCSC1) to select whether conversions will be continuous
or completed only once, and to enable or disable conversion complete interrupts. The input channel
on which conversions will be performed is also selected here.
10.5.1.2
Pseudo — Code Example
In this example, the ADC module will be set up with interrupts enabled to perform a single 10-bit
conversion at low power with a long sample time on input channel 1, where the internal ADCK clock will
be derived from the bus clock divided by 1.
ADCCFG = 0x98 (%10011000)
Bit 7
ADLPC
1
Configures for low power (lowers maximum clock speed)
Bit 6:5 ADIV
00
Sets the ADCK to the input clock ÷ 1
Bit 4
ADLSMP 1
Configures for long sample time
Bit 3:2 MODE
10
Sets mode at 10-bit conversions
Bit 1:0 ADICLK 00
Selects bus clock as input clock source
ADCSC2 = 0x00 (%00000000)
Bit 7
ADACT
0
Bit 6
ADTRG
0
Bit 5
ACFE
0
Bit 4
ACFGT
0
Bit 3:2
00
Bit 1:0
00
Flag indicates if a conversion is in progress
Software trigger selected
Compare function disabled
Not used in this example
Unimplemented or reserved, always reads zero
Reserved for Freescale’s internal use; always write zero
ADCSC1 = 0x41 (%01000001)
Bit 7
COCO
0
Bit 6
AIEN
1
Bit 5
ADCO
0
Bit 4:0 ADCH
00001
Read-only flag which is set when a conversion completes
Conversion complete interrupt enabled
One conversion only (continuous conversions disabled)
Input channel 1 selected as ADC input channel
ADCRH/L = 0xxx
Holds results of conversion. Read high byte (ADCRH) before low byte (ADCRL) so that conversion
data cannot be overwritten with data from the next conversion.
ADCCVH/L = 0xxx
Holds compare value when compare function enabled
APCTL1=0x02
AD1 pin I/O control disabled. All other AD pins remain general purpose I/O pins
APCTL2=0x00
All other AD pins remain general purpose I/O pins
MC9S08QA4 MCU Series Reference Manual, Rev. 2
132
Freescale Semiconductor
Analog-to-Digital Converter (S08ADC10V1)
RESET
INITIALIZE ADC
ADCCFG = $98
ADCSC2 = $00
ADCSC1 = $41
CHECK
COCO=1?
NO
YES
READ ADCRH
THEN ADCRL TO
CLEAR COCO BIT
CONTINUE
Figure 10-14. Initialization Flowchart for Example
10.6
Application Information
This section contains information for using the ADC module in applications. The ADC has been designed
to be integrated into a microcontroller for use in embedded control applications requiring an A/D
converter.
10.6.1
External Pins and Routing
The following sections discuss the external pins associated with the ADC module and how they should be
used for best results.
10.6.1.1
Analog Supply Pins
The ADC module has analog power and ground supplies (VDDAD and VSSAD) which are available as
separate pins on some devices. On other devices, VSSAD is shared on the same pin as the MCU digital VSS,
and on others, both VSSAD and VDDAD are shared with the MCU digital supply pins. In these cases, there
are separate pads for the analog supplies which are bonded to the same pin as the corresponding digital
supply so that some degree of isolation between the supplies is maintained.
When available on a separate pin, both VDDAD and VSSAD must be connected to the same voltage potential
as their corresponding MCU digital supply (VDD and VSS) and must be routed carefully for maximum
noise immunity and bypass capacitors placed as near as possible to the package.
MC9S08QA4 MCU Series Reference Manual, Rev. 2
Freescale Semiconductor
133
Analog-to-Digital Converter (S08ADC10V1)
In cases where separate power supplies are used for analog and digital power, the ground connection
between these supplies must be at the VSSAD pin. This should be the only ground connection between these
supplies if possible. The VSSAD pin makes a good single point ground location.
10.6.1.2
Analog Reference Pins
In addition to the analog supplies, the ADC module has connections for two reference voltage inputs. The
high reference is VREFH, which may be shared on the same pin as VDDAD on some devices. The low
reference is VREFL, which may be shared on the same pin as VSSAD on some devices.
When available on a separate pin, VREFH may be connected to the same potential as VDDAD, or may be
driven by an external source that is between the minimum VDDAD spec and the VDDAD potential (VREFH
must never exceed VDDAD). When available on a separate pin, VREFL must be connected to the same
voltage potential as VSSAD. Both VREFH and VREFL must be routed carefully for maximum noise
immunity and bypass capacitors placed as near as possible to the package.
AC current in the form of current spikes required to supply charge to the capacitor array at each successive
approximation step is drawn through the VREFH and VREFL loop. The best external component to meet this
current demand is a 0.1 μF capacitor with good high frequency characteristics. This capacitor is connected
between VREFH and VREFL and must be placed as near as possible to the package pins. Resistance in the
path is not recommended because the current will cause a voltage drop which could result in conversion
errors. Inductance in this path must be minimum (parasitic only).
10.6.1.3
Analog Input Pins
The external analog inputs are typically shared with digital I/O pins on MCU devices. The pin I/O control
is disabled by setting the appropriate control bit in one of the pin control registers. Conversions can be
performed on inputs without the associated pin control register bit set. It is recommended that the pin
control register bit always be set when using a pin as an analog input. This avoids problems with contention
because the output buffer will be in its high impedance state and the pullup is disabled. Also, the input
buffer draws dc current when its input is not at either VDD or VSS. Setting the pin control register bits for
all pins used as analog inputs should be done to achieve lowest operating current.
Empirical data shows that capacitors on the analog inputs improve performance in the presence of noise
or when the source impedance is high. Use of 0.01 μF capacitors with good high-frequency characteristics
is sufficient. These capacitors are not necessary in all cases, but when used they must be placed as near as
possible to the package pins and be referenced to VSSA.
For proper conversion, the input voltage must fall between VREFH and VREFL. If the input is equal to or
exceeds VREFH, the converter circuit converts the signal to $3FF (full scale 10-bit representation) or $FF
(full scale 8-bit representation). If the input is equal to or less than VREFL, the converter circuit converts it
to $000. Input voltages between VREFH and VREFL are straight-line linear conversions. There will be a
brief current associated with VREFL when the sampling capacitor is charging. The input is sampled for
3.5 cycles of the ADCK source when ADLSMP is low, or 23.5 cycles when ADLSMP is high.
For minimal loss of accuracy due to current injection, pins adjacent to the analog input pins should not be
transitioning during conversions.
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Analog-to-Digital Converter (S08ADC10V1)
10.6.2
Sources of Error
Several sources of error exist for A/D conversions. These are discussed in the following sections.
10.6.2.1
Sampling Error
For proper conversions, the input must be sampled long enough to achieve the proper accuracy. Given the
maximum input resistance of approximately 7kΩ and input capacitance of approximately 5.5 pF, sampling
to within 1/4LSB (at 10-bit resolution) can be achieved within the minimum sample window (3.5 cycles @
8 MHz maximum ADCK frequency) provided the resistance of the external analog source (RAS) is kept
below 5 kΩ.
Higher source resistances or higher-accuracy sampling is possible by setting ADLSMP (to increase the
sample window to 23.5 cycles) or decreasing ADCK frequency to increase sample time.
10.6.2.2
Pin Leakage Error
Leakage on the I/O pins can cause conversion error if the external analog source resistance (RAS) is high.
If this error cannot be tolerated by the application, keep RAS lower than VDDAD / (2N*ILEAK) for less than
1/4LSB leakage error (N = 8 in 8-bit mode or 10 in 10-bit mode).
10.6.2.3
Noise-Induced Errors
System noise which occurs during the sample or conversion process can affect the accuracy of the
conversion. The ADC accuracy numbers are guaranteed as specified only if the following conditions are
met:
• There is a 0.1 μF low-ESR capacitor from VREFH to VREFL.
• There is a 0.1 μF low-ESR capacitor from VDDAD to VSSAD.
• If inductive isolation is used from the primary supply, an additional 1 μF capacitor is placed from
VDDAD to VSSAD.
• VSSAD (and VREFL, if connected) is connected to VSS at a quiet point in the ground plane.
• Operate the MCU in wait or stop3 mode before initiating (hardware triggered conversions) or
immediately after initiating (hardware or software triggered conversions) the ADC conversion.
— For software triggered conversions, immediately follow the write to the ADCSC1 with a WAIT
instruction or STOP instruction.
— For stop3 mode operation, select ADACK as the clock source. Operation in stop3 reduces VDD
noise but increases effective conversion time due to stop recovery.
• There is no I/O switching, input or output, on the MCU during the conversion.
There are some situations where external system activity causes radiated or conducted noise emissions or
excessive VDD noise is coupled into the ADC. In these situations, or when the MCU cannot be placed in
wait or stop3 or I/O activity cannot be halted, these recommended actions may reduce the effect of noise
on the accuracy:
• Place a 0.01 μF capacitor (CAS) on the selected input channel to VREFL or VSSAD (this will
improve noise issues but will affect sample rate based on the external analog source resistance).
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Analog-to-Digital Converter (S08ADC10V1)
•
•
Average the result by converting the analog input many times in succession and dividing the sum
of the results. Four samples are required to eliminate the effect of a 1LSB, one-time error.
Reduce the effect of synchronous noise by operating off the asynchronous clock (ADACK) and
averaging. Noise that is synchronous to ADCK cannot be averaged out.
10.6.2.4
Code Width and Quantization Error
The ADC quantizes the ideal straight-line transfer function into 1024 steps (in 10-bit mode). Each step
ideally has the same height (1 code) and width. The width is defined as the delta between the transition
points to one code and the next. The ideal code width for an N bit converter (in this case N can be 8 or 10),
defined as 1LSB, is:
1LSB = (VREFH - VREFL) / 2N
Eqn. 10-2
There is an inherent quantization error due to the digitization of the result. For 8-bit or 10-bit conversions
the code will transition when the voltage is at the midpoint between the points where the straight line
transfer function is exactly represented by the actual transfer function. Therefore, the quantization error
will be ± 1/2LSB in 8- or 10-bit mode. As a consequence, however, the code width of the first ($000)
conversion is only 1/2LSB and the code width of the last ($FF or $3FF) is 1.5LSB.
10.6.2.5
Linearity Errors
The ADC may also exhibit non-linearity of several forms. Every effort has been made to reduce these
errors but the system should be aware of them because they affect overall accuracy. These errors are:
• Zero-scale error (EZS) (sometimes called offset) — This error is defined as the difference between
the actual code width of the first conversion and the ideal code width (1/2LSB). Note, if the first
conversion is $001, then the difference between the actual $001 code width and its ideal (1LSB) is
used.
• Full-scale error (EFS) — This error is defined as the difference between the actual code width of
the last conversion and the ideal code width (1.5LSB). Note, if the last conversion is $3FE, then the
difference between the actual $3FE code width and its ideal (1LSB) is used.
• Differential non-linearity (DNL) — This error is defined as the worst-case difference between the
actual code width and the ideal code width for all conversions.
• Integral non-linearity (INL) — This error is defined as the highest-value the (absolute value of the)
running sum of DNL achieves. More simply, this is the worst-case difference of the actual
transition voltage to a given code and its corresponding ideal transition voltage, for all codes.
• Total unadjusted error (TUE) — This error is defined as the difference between the actual transfer
function and the ideal straight-line transfer function, and therefore includes all forms of error.
10.6.2.6
Code Jitter, Non-Monotonicity and Missing Codes
Analog-to-digital converters are susceptible to three special forms of error. These are code jitter,
non-monotonicity, and missing codes.
Code jitter is when, at certain points, a given input voltage converts to one of two values when sampled
repeatedly. Ideally, when the input voltage is infinitesimally smaller than the transition voltage, the
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Analog-to-Digital Converter (S08ADC10V1)
converter yields the lower code (and vice-versa). However, even very small amounts of system noise can
cause the converter to be indeterminate (between two codes) for a range of input voltages around the
transition voltage. This range is normally around ±1/2 LSB and will increase with noise. This error may be
reduced by repeatedly sampling the input and averaging the result. Additionally the techniques discussed
in Section 10.6.2.3 will reduce this error.
Non-monotonicity is defined as when, except for code jitter, the converter converts to a lower code for a
higher input voltage. Missing codes are those values which are never converted for any input value.
In 8-bit or 10-bit mode, the ADC is guaranteed to be monotonic and to have no missing codes.
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Chapter 11
Internal Clock Source (S08ICSV1)
11.1
Introduction
The internal clock source (ICS) module provides clock source choices for the MCU. The module contains
a frequency-locked loop (FLL) as a clock source that is controllable by an internal reference clock. The
module can provide either this FLL clock or else the internal reference clock as a source for the MCU
system clock. Whichever clock source is chosen, it is passed through a reduced bus divider (BDIV) which
allows a lower final output clock frequency to be derived.
The bus frequency will be one-half of the ICSOUT frequency.
NOTE
The external reference clock is not available for the MC9S08QA4 series.
11.1.1
Module Configuration
When the internal reference is enabled in stop mode (IREFSTEN = 1), the voltage regulator must also be
enabled in stop mode by setting the LVDE and LVDSE bits in the SPMSC1 register.
On this MCU, the internal reference is not connected to any module that is operational in stop mode.
Therefore, the IREFSTEN bit in the ICSC1 register must always be cleared.
Figure 11-1 shows the MC9S08QA4 series block diagram with the ICS highlighted.
11.1.2
Factory Trim Value
A factory trim value is stored in flash during production testing. This trim value is calibrated to 31.25 kHz
at nominal VDD and temperature. To be used, this value must be copied from flash memory to the ICSTRM
register. A factory value for this FTRIM bit is also stored in flash and must be copied into the FTRIM bit
in the ICSSC register. See Table 4-4 for the flash locations of the factory ICSTRM and FTRIM values.
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Chapter 11 Internal Clock Source (S08ICSV1)
BKGD/MS
IRQ
HCS08 CORE
DEBUG MODULE (DBG)
BDC
CPU
HCS08 SYSTEM CONTROL
TCLK
PTA4/ACMPO/BKGD/MS
COP
IRQ
LVD
USER FLASH
(MC9S08QA4 = 4096 BYTES)
(MC9S08QA2 = 2048 BYTES)
USER RAM
(MC9S08QA4 = 256 BYTES)
(MC9S08QA2 = 160BYTES)
PORT A
RESETS AND INTERRUPTS
MODES OF OPERATION
POWER MANAGEMENT
RTI
PTA5//IRQ/TCLK/RESET
8-BIT MODULO TIMER
MODULE (MTIM)
PTA3/KBIP3/ADP3
PTA2/KBIP2/ADP2
4
8-BIT KEYBOARD
INTERRUPT MODULE (KBI)
ANALOG COMPARATOR
(ACMP)
ACMPO
ACMP–
ACMP+
PTA1/KBIP1/ADP1/ACMP–
PTA0/KBIP0/TPMCH0/ADP0/ACMP+
4
10-BIT
ANALOG-TO-DIGITAL
CONVERTER (ADC)
16-BIT TIMER/PWM
MODULE (TPM)
TPMCH0
16 MHz INTERNAL CLOCK
SOURCE (ICS)
VSS
VDD
VOLTAGE REGULATOR
VDDA
VSSA
VREFH
VREFL
NOTES:
1 Port pins are software configurable with pullup device if input port.
2 Port pins are software configurable for output drive strength.
3 Port pins are software configurable for output slew rate control.
4 IRQ contains a software configurable (IRQPDD) pullup device if PTA5 enabled as IRQ pin function (IRQPE = 1).
5 RESET contains integrated pullup device if PTA5 enabled as reset pin function (RSTPE = 1).
6 PTA4 contains integrated pullup device if BKGD enabled (BKGDPE = 1).
7
When pin functions as KBI (KBIPEn = 1) and associated pin is configured to enable the pullup device, KBEDGn can
be used to reconfigure the pullup as a pulldown device.
Figure 11-1. MC9S08QA4 Series Block Diagram Highlighting ICS Block
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Internal Clock Source (S08ICSV1)
11.1.3
Features
Key features of the ICS module are:
• Frequency-locked loop (FLL) is trimmable for accuracy
— 0.2% resolution using internal 32 kHz reference
— 2% deviation over voltage and temperature using internal 32 kHz reference
• External reference clock up to 5 MHz can be used to control the FLL
— 3 bit select for reference divider is provided
• Internal reference clock has 9 trim bits available
• Internal or external reference clock can be selected as the clock source for the MCU
• Whichever clock is selected as the source can be divided down
— 2 bit select for clock divider is provided
– Allowable dividers are: 1, 2, 4, 8
– BDC clock is provided as a constant divide by 2 of the DCO output
• Control signals for a low power oscillator as the external reference clock are provided
— HGO, RANGE, EREFS, ERCLKEN, EREFSTEN
• FLL engaged internal mode is automatically selected out of reset
11.1.4
Modes of Operation
The ICS features the following modes of operation: FEI, FEE, FBI, FBILP, FBE, FBELP, and stop.
11.1.4.1
FLL Engaged Internal (FEI)
In FLL engaged internal mode, which is the default mode, the ICS supplies a clock derived from the FLL
which is controlled by the internal reference clock. The BDC clock is supplied from the FLL.
11.1.4.2
FLL Engaged External (FEE)
In FLL engaged external mode, the ICS supplies a clock derived from the FLL which is controlled by an
external reference clock. The BDC clock is supplied from the FLL.
11.1.4.3
FLL Bypassed Internal (FBI)
In FLL bypassed internal mode, the FLL is enabled and controlled by the internal reference clock, but is
bypassed. The ICS supplies a clock derived from the internal reference clock. The BDC clock is supplied
from the FLL.
11.1.4.4
FLL Bypassed Internal Low Power (FBILP)
In FLL bypassed internal low power mode, the FLL is disabled and bypassed, and the ICS supplies a clock
derived from the internal reference clock. The BDC clock is not available.
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Internal Clock Source (S08ICSV1)
11.1.4.5
FLL Bypassed External (FBE)
In FLL bypassed external mode, the FLL is enabled and controlled by an external reference clock, but is
bypassed. The ICS supplies a clock derived from the external reference clock. The external reference clock
can be an external crystal/resonator supplied by an OSC controlled by the ICS, or it can be another external
clock source. The BDC clock is supplied from the FLL.
11.1.4.6
FLL Bypassed External Low Power (FBELP)
In FLL bypassed external low power mode, the FLL is disabled and bypassed, and the ICS supplies a clock
derived from the external reference clock. The external reference clock can be an external crystal/resonator
supplied by an OSC controlled by the ICS, or it can be another external clock source. The BDC clock is
not available.
11.1.4.7
Stop (STOP)
In stop mode, the FLL is disabled and the internal or external reference clock can be selected to be enabled
or disabled. The BDC clock is not available. ICS does not provide an MCU clock source.
11.1.5
Block Diagram
This section contains the ICS block diagram.
Optional
External Reference
Clock Source
Block
RANGE
HGO
EREFS
EREFSTEN
ICSERCLK
ERCLKEN
IRCLKEN
IREFSTEN
ICSIRCLK
CLKS
BDIV
/ 2n
Internal
Reference
Clock
9
IREFS
ICSOUT
n=0-3
LP
DCO
DCOOUT
/2
ICSLCLK
TRIM
ICSFFCLK
9
/ 2n
RDIV_CLK
Filter
n=0-7
FLL
RDIV
Internal Clock Source Block
Figure 11-2. Internal Clock Source (ICS) Block Diagram
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Internal Clock Source (S08ICSV1)
11.2
External Signal Description
No ICS signal connects off chip.
11.3
Register Definition
11.3.1
ICS Control Register 1 (ICSC1)
7
6
5
4
3
2
1
0
IREFS
IRCLKEN
IREFSTEN
1
0
0
R
CLKS
RDIV
W
Reset:
0
0
0
0
0
Figure 11-3. ICS Control Register 1 (ICSC1)
Table 11-1. ICS Control Register 1 Field Descriptions
Field
Description
7:6
CLKS
Clock Source Select — Selects the clock source that controls the bus frequency. The actual bus frequency
depends on the value of the BDIV bits.
00 Output of FLL is selected.
01 Internal reference clock is selected.
10 External reference clock is selected.
11 Reserved, defaults to 00.
5:3
RDIV
Reference Divider — Selects the amount to divide down the FLL reference clock selected by the IREFS bits.
Resulting frequency must be in the range 31.25 kHz to 39.0625 kHz.
000 Encoding 0 — Divides reference clock by 1 (reset default)
001 Encoding 1 — Divides reference clock by 2
010 Encoding 2 — Divides reference clock by 4
011 Encoding 3 — Divides reference clock by 8
100 Encoding 4 — Divides reference clock by 16
101 Encoding 5 — Divides reference clock by 32
110 Encoding 6 — Divides reference clock by 64
111 Encoding 7 — Divides reference clock by 128
2
IREFS
Internal Reference Select — The IREFS bit selects the reference clock source for the FLL.
1 Internal reference clock selected
0 External reference clock selected
1
IRCLKEN
0
IREFSTEN
Internal Reference Clock Enable — The IRCLKEN bit enables the internal reference clock for use as
ICSIRCLK.
1 ICSIRCLK active
0 ICSIRCLK inactive
Internal Reference Stop Enable — The IREFSTEN bit controls whether or not the internal reference clock
remains enabled when the ICS enters stop mode.
1 Internal reference clock stays enabled in stop if IRCLKEN is set or if ICS is in FEI, FBI, or FBILP mode before
entering stop
0 Internal reference clock is disabled in stop
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Internal Clock Source (S08ICSV1)
11.3.2
ICS Control Register 2 (ICSC2)
7
6
5
4
3
2
RANGE
HGO
LP
EREFS
0
0
0
0
1
0
R
BDIV
ERCLKEN EREFSTEN
W
Reset:
0
1
0
0
Figure 11-4. ICS Control Register 2 (ICSC2)
Table 11-2. ICS Control Register 2 Field Descriptions
Field
Description
7:6
BDIV
Bus Frequency Divider — Selects the amount to divide down the clock source selected by the CLKS bits. This
controls the bus frequency.
00 Encoding 0 — Divides selected clock by 1
01 Encoding 1 — Divides selected clock by 2 (reset default)
10 Encoding 2 — Divides selected clock by 4
11 Encoding 3 — Divides selected clock by 8
5
RANGE
Frequency Range Select — Selects the frequency range for the external oscillator.
1 High frequency range selected for the external oscillator
0 Low frequency range selected for the external oscillator
4
HGO
High Gain Oscillator Select — The HGO bit controls the external oscillator mode of operation.
1 Configure external oscillator for high gain operation
0 Configure external oscillator for low power operation
3
LP
Low Power Select — The LP bit controls whether the FLL is disabled in FLL bypassed modes.
1 FLL is disabled in bypass modes unless BDM is active
0 FLL is not disabled in bypass mode
2
EREFS
1
ERCLKEN
External Reference Select — The EREFS bit selects the source for the external reference clock.
1 Oscillator requested
0 External Clock Source requested
External Reference Enable — The ERCLKEN bit enables the external reference clock for use as ICSERCLK.
1 ICSERCLK active
0 ICSERCLK inactive
0
External Reference Stop Enable — The EREFSTEN bit controls whether or not the external reference clock
EREFSTEN remains enabled when the ICS enters stop mode.
1 External reference clock stays enabled in stop if ERCLKEN is set or if ICS is in FEE, FBE, or FBELP mode
before entering stop
0 External reference clock is disabled in stop
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Internal Clock Source (S08ICSV1)
11.3.3
ICS Trim Register (ICSTRM)
7
6
5
4
3
2
1
0
R
TRIM
W
POR:
1
0
0
0
0
0
0
0
Reset:
U
U
U
U
U
U
U
U
Figure 11-5. ICS Trim Register (ICSTRM)
Table 11-3. ICS Trim Register Field Descriptions
Field
Description
7:0
TRIM
ICS Trim Setting — The TRIM bits control the internal reference clock frequency by controlling the internal
reference clock period. The bits’ effect are binary weighted (i.e., bit 1 will adjust twice as much as bit 0).
Increasing the binary value in TRIM will increase the period, and decreasing the value will decrease the period.
An additional fine trim bit is available in ICSSC as the FTRIM bit.
11.3.4
ICS Status and Control (ICSSC)
R
7
6
5
4
0
0
0
0
3
2
CLKST
1
0
OSCINIT
FTRIM
W
POR:
Reset:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
U
Figure 11-6. ICS Status and Control Register (ICSSC)
Table 11-4. ICS Status and Control Register Field Descriptions
Field
Description
3:2
CLKST
Clock Mode Status — The CLKST bits indicate the current clock mode. The CLKST bits don’t update
immediately after a write to the CLKS bits due to internal synchronization between clock domains.
00 Output of FLL is selected.
01 FLL Bypassed, Internal reference clock is selected.10FLL Bypassed, External reference clock is selected.
11
Reserved.
1
OSC Initialization — If the external reference clock is selected by ERCLKEN or by the ICS being in FEE, FBE,
or FBELP mode, and if EREFS is set, then this bit is set after the initialization cycles of the external oscillator
clock have completed. This bit is only cleared when either ERCLKEN or EREFS are cleared.
FTRIM
0
ICS Fine Trim — The FTRIM bit controls the smallest adjustment of the internal reference clock frequency.
Setting FTRIM will increase the period and clearing FTRIM will decrease the period by the smallest amount
possible.
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Internal Clock Source (S08ICSV1)
11.4
Functional Description
11.4.1
Operational Modes
The states of the ICS are shown as a state diagram and are described in the following sections. The arrows
indicate the allowed movements between the states.
IREFS=1
CLKS=00
FLL Engaged
Internal (FEI)
IREFS=0
CLKS=10BDM Enabled
or LP =0
FLL Bypassed
External Low
Power(FBELP)
FLL Bypassed
External (FBE)
IREFS=0
CLKS=10
BDM Disabled
and LP=1
IREFS=1
CLKS=01
BDM Enabled
or LP=0
FLL Bypassed
Internal (FBI)
FLL Bypassed
Internal Low
Power(FBILP)
IREFS=1
CLKS=01
BDM Disabled
and LP=1
FLL Engaged
External (FEE)
IREFS=0
CLKS=00
Entered from any state
when MCU enters stop
Stop
Returns to state that was active
before MCU entered stop, unless
RESET occurs while in stop.
Figure 11-7. Clock Switching Modes
11.4.1.1
FLL Engaged Internal (FEI)
FLL engaged internal (FEI) is the default mode of operation out of any reset and is entered when all the
following conditions occur:
• CLKS bits are written to 00
• IREFS bit is written to 1
• RDIV bits are written to divide reference clock to be within the range of 31.25 kHz to 39.0625 kHz.
In FLL engaged internal mode, the ICSOUT clock is derived from the FLL clock, which is controlled by
the internal reference clock. The FLL loop will lock the frequency to 512 times the filter frequency, as
selected by the RDIV bits. The ICSLCLK is available for BDC communications, and the internal reference
clock is enabled.
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Internal Clock Source (S08ICSV1)
11.4.1.2
FLL Engaged External (FEE)
The FLL engaged external (FEE) mode is entered when all the following conditions occur:
•
•
•
CLKS bits are written to 00
IREFS bit is written to 0
RDIV bits are written to divide reference clock to be within the range of 31.25 kHz to 39.0625 kHz
In FLL engaged external mode, the ICSOUT clock is derived from the FLL clock which is controlled by
the external reference clock.The FLL loop will lock the frequency to 512 times the filter frequency, as
selected by the RDIV bits. The ICSLCLK is available for BDC communications, and the external
reference clock is enabled.
11.4.1.3
FLL Bypassed Internal (FBI)
The FLL bypassed internal (FBI) mode is entered when all the following conditions occur:
• CLKS bits are written to 01
• IREFS bit is written to 1
• BDM mode is active or LP bit is written to 0
In FLL bypassed internal mode, the ICSOUT clock is derived from the internal reference clock. The FLL
clock is controlled by the internal reference clock, and the FLL loop will lock the FLL frequency to 512
times the filter frequency, as selected by the RDIV bits. The ICSLCLK will be available for BDC
communications, and the internal reference clock is enabled.
11.4.1.4
FLL Bypassed Internal Low Power (FBILP)
The FLL bypassed internal low power (FBILP) mode is entered when all the following conditions occur:
• CLKS bits are written to 01
• IREFS bit is written to 1.
• BDM mode is not active and LP bit is written to 1
In FLL bypassed internal low power mode, the ICSOUT clock is derived from the internal reference clock
and the FLL is disabled. The ICSLCLK will be not be available for BDC communications, and the internal
reference clock is enabled.
11.4.1.5
FLL Bypassed External (FBE)
The FLL bypassed external (FBE) mode is entered when all the following conditions occur:
• CLKS bits are written to 10.
• IREFS bit is written to 0.
• BDM mode is active or LP bit is written to 0.
In FLL bypassed external mode, the ICSOUT clock is derived from the external reference clock. The FLL
clock is controlled by the external reference clock, and the FLL loop will lock the FLL frequency to 512
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Internal Clock Source (S08ICSV1)
times the filter frequency, as selected by the RDIV bits, so that the ICSLCLK will be available for BDC
communications, and the external reference clock is enabled.
11.4.1.6
FLL Bypassed External Low Power (FBELP)
The FLL bypassed external low power (FBELP) mode is entered when all the following conditions occur:
• CLKS bits are written to 10.
• IREFS bit is written to 0.
• BDM mode is not active and LP bit is written to 1.
In FLL bypassed external low power mode, the ICSOUT clock is derived from the external reference clock
and the FLL is disabled. The ICSLCLK will be not be available for BDC communications. The external
reference clock is enabled.
11.4.1.7
Stop
ICS stop mode is entered whenever the MCU enters stop. In this mode, all ICS clock signals are stopped
except in the following cases:
ICSIRCLK will be active in stop mode when all the following conditions occur:
• IRCLKEN bit is written to 1
• IREFSTEN bit is written to 1
ICSERCLK will be active in stop mode when all the following conditions occur:
• ERCLKEN bit is written to 1
• EREFSTEN bit is written to 1
11.4.2
Mode Switching
When switching between FLL engaged internal (FEI) and FLL engaged external (FEE) modes the IREFS
bit can be changed at anytime, but the RDIV bits must be changed simultaneously so that the resulting
frequency stays in the range of 31.25 kHz to 39.0625 kHz. After a change in the IREFS value the FLL will
begin locking again after a few full cycles of the resulting divided reference frequency.
The CLKS bits can also be changed at anytime, but the RDIV bits must be changed simultaneously so that
the resulting frequency stays in the range of 31.25 kHz to 39.0625 kHz. The actual switch to the newly
selected clock will not occur until after a few full cycles of the new clock. If the newly selected clock is
not available, the previous clock will remain selected.
11.4.3
Bus Frequency Divider
The BDIV bits can be changed at anytime and the actual switch to the new frequency will occur
immediately.
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11.4.4
Low Power Bit Usage
The low power bit (LP) is provided to allow the FLL to be disabled and thus conserve power when it is
not being used. However, in some applications it may be desirable to enable the FLL and allow it to lock
for maximum accuracy before switching to an FLL engaged mode. Do this by writing the LP bit to 0.
11.4.5
Internal Reference Clock
When IRCLKEN is set the internal reference clock signal will be presented as ICSIRCLK, which can be
used as an additional clock source. The ICSIRCLK frequency can be re-targeted by trimming the period
of the internal reference clock. This can be done by writing a new value to the TRIM bits in the ICSTRM
register. Writing a larger value will slow down the ICSIRCLK frequency, and writing a smaller value to
the ICSTRM register will speed up the ICSIRCLK frequency. The TRIM bits will effect the ICSOUT
frequency if the ICS is in FLL engaged internal (FEI), FLL bypassed internal (FBI), or FLL bypassed
internal low power (FBILP) mode. The TRIM and FTRIM value will not be affected by a reset.
Until ICSIRCLK is trimmed, programming low reference divider (RDIV) factors may result in ICSOUT
frequencies that exceed the maximum chip-level frequency and violate the chip-level clock timing
specifications (see the Device Overview chapter).
If IREFSTEN is set and the IRCLKEN bit is written to 1, the internal reference clock will keep running
during stop mode in order to provide a fast recovery upon exiting stop.
All MCU devices are factory programmed with a trim value in a reserved memory location. This value can
be copied to the ICSTRM register during reset initialization. The factory trim value does not include the
FTRIM bit. For finer precision, the user can trim the internal oscillator in the application and set the
FTRIM bit accordingly.
11.4.6
Optional External Reference Clock
The ICS module can support an external reference clock with frequencies between 31.25 kHz to 5 MHz
in all modes. When the ERCLKEN is set, the external reference clock signal will be presented as
ICSERCLK, which can be used as an additional clock source. When IREFS = 1, the external reference
clock will not be used by the FLL and will only be used as ICSERCLK. In these modes, the frequency can
be equal to the maximum frequency the chip-level timing specifications will support (see the Device
Overview chapter).
If EREFSTEN is set and the ERCLKEN bit is written to 1, the external reference clock will keep running
during stop mode in order to provide a fast recovery upon exiting stop.
11.4.7
Fixed Frequency Clock
The ICS provides the divided FLL reference clock as ICSFFCLK for use as an additional clock source for
peripheral modules. The ICS provides an output signal (ICSFFE) which indicates when the ICS is
providing ICSOUT frequencies four times or greater than the divided FLL reference clock (ICSFFCLK).
In FLL engaged mode (FEI and FEE), this is always true and ICSFFE is always high. In ICS Bypass
modes, ICSFFE will get asserted for the following combinations of BDIV and RDIV values:
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Internal Clock Source (S08ICSV1)
•
•
•
•
BDIV=00 (divide by 1), RDIV ≥ 010
BDIV=01 (divide by 2), RDIV ≥ 011
BDIV=10 (divide by 4), RDIV ≥ 100
BDIV=11 (divide by 8), RDIV ≥ 101
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Chapter 12
Modulo Timer (S08MTIMV1)
12.1
Introduction
The MTIM is a simple 8-bit timer with several software selectable clock sources and a programmable
interrupt.
The central component of the MTIM is the 8-bit counter, which can operate as a free-running counter or a
modulo counter. A timer overflow interrupt can be enabled to generate periodic interrupts for time-based
software loops.
Figure 12-1 shows the MC9S08QA4 series block diagram with the MTIM highlighted.
12.1.1
MTIM/TPM Configuration Information
The external clock for the MTIM module, TCLK, is selected by setting CLKS = 1:1 or 1:0 in MTIMCLK,
which selects the TCLK pin input. The TCLK input on PTA5 can be enabled as external clock inputs to
both the MTIM and TPM modules simultaneously.
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Chapter 12 Modulo Timer (S08MTIMV1)
BKGD/MS
IRQ
HCS08 CORE
DEBUG MODULE (DBG)
BDC
CPU
HCS08 SYSTEM CONTROL
TCLK
PTA4/ACMPO/BKGD/MS
COP
IRQ
LVD
USER FLASH
(MC9S08QA4 = 4096 BYTES)
(MC9S08QA2 = 2048 BYTES)
USER RAM
(MC9S08QA4 = 256 BYTES)
(MC9S08QA2 = 160BYTES)
PORT A
RESETS AND INTERRUPTS
MODES OF OPERATION
POWER MANAGEMENT
RTI
PTA5//IRQ/TCLK/RESET
8-BIT MODULO TIMER
MODULE (MTIM)
PTA3/KBIP3/ADP3
PTA2/KBIP2/ADP2
4
8-BIT KEYBOARD
INTERRUPT MODULE (KBI)
ANALOG COMPARATOR
(ACMP)
ACMPO
ACMP–
ACMP+
PTA1/KBIP1/ADP1/ACMP–
PTA0/KBIP0/TPMCH0/ADP0/ACMP+
4
10-BIT
ANALOG-TO-DIGITAL
CONVERTER (ADC)
16-BIT TIMER/PWM
MODULE (TPM)
TPMCH0
16 MHz INTERNAL CLOCK
SOURCE (ICS)
VSS
VDD
VOLTAGE REGULATOR
VDDA
VSSA
VREFH
VREFL
NOTES:
1 Port pins are software configurable with pullup device if input port.
2 Port pins are software configurable for output drive strength.
3 Port pins are software configurable for output slew rate control.
4 IRQ contains a software configurable (IRQPDD) pullup device if PTA5 enabled as IRQ pin function (IRQPE = 1).
5 RESET contains integrated pullup device if PTA5 enabled as reset pin function (RSTPE = 1).
6 PTA4 contains integrated pullup device if BKGD enabled (BKGDPE = 1).
7
When pin functions as KBI (KBIPEn = 1) and associated pin is configured to enable the pullup device, KBEDGn can
be used to reconfigure the pullup as a pulldown device.
Figure 12-1. MC9S08QA4 Series Block Diagram Highlighting MTIM Block and Pins
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Modulo Timer (S08MTIMV1)
12.1.2
Features
Timer system features include:
• 8-bit up-counter
— Free-running or 8-bit modulo limit
— Software controllable interrupt on overflow
— Counter reset bit (TRST)
— Counter stop bit (TSTP)
• Four software selectable clock sources for input to prescaler:
— System bus clock — rising edge
— Fixed frequency clock (XCLK) — rising edge
— External clock source on the TCLK pin — rising edge
— External clock source on the TCLK pin — falling edge
• Nine selectable clock prescale values:
— Clock source divide by 1, 2, 4, 8, 16, 32, 64, 128, or 256
12.1.3
Modes of Operation
This section defines the MTIM’s operation in stop, wait and background debug modes.
12.1.3.1
MTIM in Wait Mode
The MTIM continues to run in wait mode if enabled before executing the WAIT instruction. Therefore,
the MTIM can be used to bring the MCU out of wait mode if the timer overflow interrupt is enabled. For
lowest possible current consumption, the MTIM should be stopped by software if not needed as an
interrupt source during wait mode.
12.1.3.2
MTIM in Stop Modes
The MTIM is disabled in all stop modes, regardless of the settings before executing the STOP instruction.
Therefore, the MTIM cannot be used as a wake up source from stop modes.
Waking from stop1 and stop2 modes, the MTIM will be put into its reset state. If stop3 is exited with a
reset, the MTIM will be put into its reset state. If stop3 is exited with an interrupt, the MTIM continues
from the state it was in when stop3 was entered. If the counter was active upon entering stop3, the count
will resume from the current value.
12.1.3.3
MTIM in Active Background Mode
The MTIM suspends all counting until the microcontroller returns to normal user operating mode.
Counting resumes from the suspended value as long as an MTIM reset did not occur (TRST written to a 1
or MTIM1MOD written).
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Modulo Timer (S08MTIMV1)
12.1.4
Block Diagram
The block diagram for the modulo timer module is shown Figure 12-2.
BUSCLK
XCLK
TCLK
SYNC
MTIM1
INTERRU
PT
CLOCK
SOURCE
SELECT
PRESCALE
AND SELECT
DIVIDE BY
CLKS
PS
8-BIT COUNTER
(MTIM1CNT)
TRST
TSTP
8-BIT COMPARATOR
TOF
8-BIT MODULO
(MTIM1MOD)
TOIE
Figure 12-2. Modulo Timer (MTIM) Block Diagram
12.2
External Signal Description
The MTIM includes one external signal, TCLK, used to input an external clock when selected as the
MTIM clock source. The signal properties of TCLK are shown in Table 12-1.
Table 12-1. Signal Properties
Signal
TCLK
Function
External clock source input into MTIM
I/O
I
The TCLK input must be synchronized by the bus clock. Also, variations in duty cycle and clock jitter
must be accommodated. Therefore, the TCLK signal must be limited to one-fourth of the bus frequency.
The TCLK pin can be muxed with a general-purpose port pin. See the Pins and Connections chapter for
the pin location and priority of this function.
12.3
Register Definition
Figure 12-3 is a summary of MTIM registers.
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Modulo Timer (S08MTIMV1)
Figure 12-3. MTIM1 Register Summary
Name
7
R
6
TOF
MTIM1SC
5
4
0
TOIE
W
R
3
2
1
0
0
0
0
0
TSTP
TRST
0
MTIM1CLK
0
CLKS
PS
W
R
COUNT
MTIM1CNT
W
R
MTIM1MOD
MOD
W
Each MTIM includes four registers:
• An 8-bit status and control register
• An 8-bit clock configuration register
• An 8-bit counter register
• An 8-bit modulo register
Refer to the direct-page register summary in the Memory chapter of this data sheet for the absolute address
assignments for all MTIM registers.This section refers to registers and control bits only by their names and
relative address offsets.
Some MCUs may have more than one MTIM, so register names include placeholder characters to identify
which MTIM is being referenced.
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Modulo Timer (S08MTIMV1)
12.3.1
MTIM1 Status and Control Register (MTIM1SC)
MTIM1SC contains the overflow status flag and control bits which are used to configure the interrupt enable,
reset the counter, and stop the counter.
7
R
6
5
TOF
0
TOIE
W
Reset:
4
3
2
1
0
0
0
0
0
0
0
0
0
TSTP
TRST
0
0
0
1
Figure 12-4. MTIM1 Status and Control Register
Table 12-2. MTIM1 Status and Control Register Field Descriptions
Field
Description
7
TOF
MTIM Overflow Flag — This read-only bit is set when the MTIM counter register overflows to $00 after reaching
the value in the MTIM modulo register. Clear TOF by reading the MTIM1SC register while TOF is set, then writing
a 0 to TOF. TOF is also cleared when TRST is written to a 1 or when any value is written to the MTIM1MOD register.
0 MTIM counter has not reached the overflow value in the MTIM modulo register.
1 MTIM counter has reached the overflow value in the MTIM modulo register.
6
TOIE
MTIM Overflow Interrupt Enable — This read/write bit enables MTIM overflow interrupts. If TOIE is set, then an
interrupt is generated when TOF = 1. Reset clears TOIE. Do not set TOIE if TOF = 1. Clear TOF first, then set TOIE.
0 TOF interrupts are disabled. Use software polling.
1 TOF interrupts are enabled.
5
TRST
MTIM Counter Reset — When a 1 is written to this write-only bit, the MTIM counter register resets to $00 and TOF
is cleared. Reading this bit always returns 0.
0 No effect. MTIM counter remains at current state.
1 MTIM counter is reset to $00.
4
TSTP
MTIM Counter Stop — When set, this read/write bit stops the MTIM counter at its current value. Counting resumes
from the current value when TSTP is cleared. Reset sets TSTP to prevent the MTIM from counting.
0 MTIM counter is active.
1 MTIM counter is stopped.
3:0
Unused register bits, always read 0.
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Modulo Timer (S08MTIMV1)
12.3.2
MTIM1 Clock Configuration Register (MTIM1CLK)
MTIM1CLK contains the clock select bits (CLKS) and the prescaler select bits (PS).
R
7
6
0
0
5
4
3
2
CLKS
1
0
0
0
PS
W
Reset:
0
0
0
0
0
0
Figure 12-5. MTIM1 Clock Configuration Register
Table 12-3. MTIM1 Clock Configuration Register Field Description
Field
7:6
5:4
CLKS
3:0
PS
Description
Unused register bits, always read 0.
Clock Source Select — These two read/write bits select one of four different clock sources as the input to the
MTIM prescaler. Changing the clock source while the counter is active does not clear the counter. The count
continues with the new clock source. Reset clears CLKS to 000.
00
Encoding 0. Bus clock (BUSCLK)
01
Encoding 1. Fixed-frequency clock (XCLK)
10
Encoding 3. External source (TCLK pin), falling edge
11
Encoding 4. External source (TCLK pin), rising edge
All other encodings default to the bus clock (BUSCLK).
Clock Source Prescaler — These four read/write bits select one of nine outputs from the 8-bit prescaler. Changing
the prescaler value while the counter is active does not clear the counter. The count continues with the new
prescaler value. Reset clears PS to 0000.
0000 Encoding 0. MTIM clock source ÷ 1
0001 Encoding 1. MTIM clock source ÷ 2
0010 Encoding 2. MTIM clock source ÷ 4
0011 Encoding 3. MTIM clock source ÷ 8
0100 Encoding 4. MTIM clock source ÷ 16
0101 Encoding 5. MTIM clock source ÷ 32
0110 Encoding 6. MTIM clock source ÷ 64
0111 Encoding 7. MTIM clock source ÷ 128
1000 Encoding 8. MTIM clock source ÷ 256
All other encodings default to MTIM clock source ÷ 256.
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Modulo Timer (S08MTIMV1)
12.3.3
MTIM1 Counter Register (MTIM1CNT)
MTIM1CNT
is the read-only value of the current MTIM count of the 8-bit counter.
7
6
5
4
R
3
2
1
0
0
0
0
0
COUNT
W
Reset:
0
0
0
0
Figure 12-6. MTIM1 Counter Register
Table 12-4. MTIM1 Counter Register Field Description
Field
Description
7:0
COUNT
MTIM Count — These eight read-only bits contain the current value of the 8-bit counter. Writes have no effect to
this register. Reset clears the count to $00.
12.3.4
MTIM1 Modulo Register (MTIM1MOD)
7
6
5
4
3
2
1
0
0
0
0
0
R
MOD
W
Reset:
0
0
0
0
Figure 12-7. MTIM1 Modulo Register
Table 12-5. MTIM1 Modulo Register Field Descriptions
Field
Description
7:0
MOD
MTIM Modulo — These eight read/write bits contain the modulo value used to reset the count and set TOF. A value
of $00 puts the MTIM in free-running mode. Writing to MTIM1MOD resets the COUNT to $00 and clears TOF.
Reset sets the modulo to $00.
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Modulo Timer (S08MTIMV1)
12.4
Functional Description
The MTIM is composed of a main 8-bit up-counter with an 8-bit modulo register, a clock source selector,
and a prescaler block with nine selectable values. The module also contains software selectable interrupt
logic.
The MTIM counter (MTIM1CNT) has three modes of operation: stopped, free-running, and modulo. Out of
reset, the counter is stopped. If the counter is started without writing a new value to the modulo register,
then the counter will be in free-running mode. The counter is in modulo mode when a value other than $00
is in the modulo register while the counter is running.
After any MCU reset, the counter is stopped and reset to $00, and the modulus is set to $00. The bus clock
is selected as the default clock source and the prescale value is divide by 1. To start the MTIM in
free-running mode, simply write to the MTIM status and control register (MTIM1SC) and clear the MTIM
stop bit (TSTP).
Four clock sources are software selectable: the internal bus clock, the fixed frequency clock (XCLK), and
an external clock on the TCLK pin, selectable as incrementing on either rising or falling edges. The MTIM
clock select bits (CLKS1:CLKS0) in MTIM1SC are used to select the desired clock source. If the counter is
active (TSTP = 0) when a new clock source is selected, the counter will continue counting from the
previous value using the new clock source.
Nine prescale values are software selectable: clock source divided by 1, 2, 4, 8, 16, 32, 64, 128, or 256.
The prescaler select bits (PS[3:0]) in MTIM1SC select the desired prescale value. If the counter is active
(TSTP = 0) when a new prescaler value is selected, the counter will continue counting from the previous
value using the new prescaler value.
The MTIM modulo register (MTIM1MOD) allows the overflow compare value to be set to any value from
$01 to $FF. Reset clears the modulo value to $00, which results in a free running counter.
When the counter is active (TSTP = 0), the counter increments at the selected rate until the count matches
the modulo value. When these values match, the counter overflows to $00 and continues counting. The
MTIM overflow flag (TOF) is set whenever the counter overflows. The flag sets on the transition from the
modulo value to $00. Writing to MTIM1MOD while the counter is active resets the counter to $00 and clears
TOF.
Clearing TOF is a two-step process. The first step is to read the MTIM1SC register while TOF is set. The
second step is to write a 0 to TOF. If another overflow occurs between the first and second steps, the
clearing process is reset and TOF will remain set after the second step is performed. This will prevent the
second occurrence from being missed. TOF is also cleared when a 1 is written to TRST or when any value
is written to the MTIM1MOD register.
The MTIM allows for an optional interrupt to be generated whenever TOF is set. To enable the MTIM
overflow interrupt, set the MTIM overflow interrupt enable bit (TOIE) in MTIM1SC. TOIE should never be
written to a 1 while TOF = 1. Instead, TOF should be cleared first, then the TOIE can be set to 1.
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Modulo Timer (S08MTIMV1)
12.4.1
MTIM Operation Example
This section shows an example of the MTIM operation as the counter reaches a matching value from the
modulo register.
selected
clock source
MTIM clock
(PS=%0010)
MTIM1CNT
$A7
$A8
$A9
$AA
$00
$01
TOF
MTIM1MOD:
$AA
Figure 12-8. MTIM counter overflow example
In the example of Figure 12-8, the selected clock source could be any of the five possible choices. The
prescaler is set to PS = %0010 or divide-by-4. The modulo value in the MTIM1MOD register is set to $AA.
When the counter, MTIM1CNT, reaches the modulo value of $AA, the counter overflows to $00 and
continues counting. The timer overflow flag, TOF, sets when the counter value changes from $AA to $00.
An MTIM overflow interrupt is generated when TOF is set, if TOIE = 1.
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Chapter 13
Timer/Pulse-Width Modulator (S08TPMV2)
13.1
Introduction
Figure 13-1 shows the MC9S08QA4 series block diagram with the TPM highlighted.
13.1.1
ACMP/TPM Configuration Information
The ACMP module can be configured to connect the output of the analog comparator to TPM input capture
channel 0 by setting ACIC in SOPT2. With ACIC set, the TPMCH0 pin is not available externally
regardless of the configuration of the TPM module.
13.1.2
MTIM/TPM Configuration Information
The external clock for the TPM module, TPMCLK, is selected by setting CLKS[B:A] = 1:1 in TPMSC,
which selects the TCLK pin input. The TCLK input on PTA5 can be enabled as external clock inputs to
both the MTIM and TPM modules simultaneously.
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Chapter 13 Timer/Pulse-Width Modulator (S08TPMV2)
BKGD/MS
IRQ
HCS08 CORE
DEBUG MODULE (DBG)
BDC
CPU
HCS08 SYSTEM CONTROL
TCLK
PTA4/ACMPO/BKGD/MS
COP
IRQ
LVD
USER FLASH
(MC9S08QA4 = 4096 BYTES)
(MC9S08QA2 = 2048 BYTES)
USER RAM
(MC9S08QA4 = 256 BYTES)
(MC9S08QA2 = 160BYTES)
PORT A
RESETS AND INTERRUPTS
MODES OF OPERATION
POWER MANAGEMENT
RTI
PTA5//IRQ/TCLK/RESET
8-BIT MODULO TIMER
MODULE (MTIM)
PTA3/KBIP3/ADP3
PTA2/KBIP2/ADP2
4
8-BIT KEYBOARD
INTERRUPT MODULE (KBI)
ANALOG COMPARATOR
(ACMP)
ACMPO
ACMP–
ACMP+
PTA1/KBIP1/ADP1/ACMP–
PTA0/KBIP0/TPMCH0/ADP0/ACMP+
4
10-BIT
ANALOG-TO-DIGITAL
CONVERTER (ADC)
16-BIT TIMER/PWM
MODULE (TPM)
TPMCH0
16 MHz INTERNAL CLOCK
SOURCE (ICS)
VSS
VDD
VOLTAGE REGULATOR
VDDA
VSSA
VREFH
VREFL
NOTES:
1 Port pins are software configurable with pullup device if input port.
2 Port pins are software configurable for output drive strength.
3 Port pins are software configurable for output slew rate control.
4 IRQ contains a software configurable (IRQPDD) pullup device if PTA5 enabled as IRQ pin function (IRQPE = 1).
5 RESET contains integrated pullup device if PTA5 enabled as reset pin function (RSTPE = 1).
6 PTA4 contains integrated pullup device if BKGD enabled (BKGDPE = 1).
7
When pin functions as KBI (KBIPEn = 1) and associated pin is configured to enable the pullup device, KBEDGn can
be used to reconfigure the pullup as a pulldown device.
Figure 13-1. MC9S08QA4 Series Block Diagram Highlighting TPM Block and Pins
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Timer/Pulse-Width Modulator (S08TPMV2)
13.1.3
Features
The TPM has the following features:
• Each TPM may be configured for buffered, center-aligned pulse-width modulation (CPWM) on all
channels
• Clock sources independently selectable per TPM (multiple TPMs device)
• Selectable clock sources (device dependent): bus clock, fixed system clock, external pin
• Clock prescaler taps for divide by 1, 2, 4, 8, 16, 32, 64, or 128
• 16-bit free-running or up/down (CPWM) count operation
• 16-bit modulus register to control counter range
• Timer system enable
• One interrupt per channel plus a terminal count interrupt for each TPM module (multiple TPMs
device)
• Channel features:
— Each channel may be input capture, output compare, or buffered edge-aligned PWM
— Rising-edge, falling-edge, or any-edge input capture trigger
— Set, clear, or toggle output compare action
— Selectable polarity on PWM outputs
13.1.4
Block Diagram
Figure 13-2 shows the structure of a TPM. Some MCUs include more than one TPM, with various
numbers of channels.
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Timer/Pulse-Width Modulator (S08TPMV2)
BUSCLK
XCLK
TPMxCLK
SYNC
CLOCK SOURCE
SELECT
OFF, BUS, XCLK, EXT
CLKSB
PRESCALE AND SELECT
DIVIDE BY
1, 2, 4, 8, 16, 32, 64, or 128
PS2
CLKSA
PS1
PS0
CPWMS
MAIN 16-BIT COUNTER
TOF
COUNTER RESET
INTERRUPT
LOGIC
TOIE
16-BIT COMPARATOR
TPMxMODH:TPMxMODL
ELS0B
CHANNEL 0
ELS0A
PORT
LOGIC
16-BIT COMPARATOR
TPMxC0VH:TPMxC0VL
CH0F
INTERRUPT
LOGIC
MS0B
MS0A
ELS1B
ELS1A
CH0IE
TPMxC1VH:TPMxC1VL
CH1F
INTERRUPT
LOGIC
16-BIT LATCH
MS1A
ELSnB
ELSnA
...
MS1B
CH1IE
...
CHANNEL n
TPMxCH1
PORT
LOGIC
16-BIT COMPARATOR
...
INTERNAL BUS
16-BIT LATCH
CHANNEL 1
TPMxCH0
TPMxCnVH:TPMxCnVL
TPMxCHn
PORT
LOGIC
16-BIT COMPARATOR
CHnF
16-BIT LATCH
MSnB
MSnA
CHnIE
INTERRUPT
LOGIC
Figure 13-2. TPM Block Diagram
The central component of the TPM is the 16-bit counter that can operate as a free-running counter, a
modulo counter, or an up-/down-counter when the TPM is configured for center-aligned PWM. The TPM
counter (when operating in normal up-counting mode) provides the timing reference for the input capture,
output compare, and edge-aligned PWM functions. The timer counter modulo registers,
TPMxMODH:TPMxMODL, control the modulo value of the counter. (The values 0x0000 or 0xFFFF
effectively make the counter free running.) Software can read the counter value at any time without
affecting the counting sequence. Any write to either byte of the TPMxCNT counter resets the counter
regardless of the data value written.
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Timer/Pulse-Width Modulator (S08TPMV2)
All TPM channels are programmable independently as input capture, output compare, or buffered
edge-aligned PWM channels.
13.2
External Signal Description
When any pin associated with the timer is configured as a timer input, a passive pullup can be enabled.
After reset, the TPM modules are disabled and all pins default to general-purpose inputs with the passive
pullups disabled.
13.2.1
External TPM Clock Sources
When control bits CLKSB:CLKSA in the timer status and control register are set to 1:1, the prescaler and
consequently the 16-bit counter for TPMx are driven by an external clock source, TPMxCLK, connected
to an I/O pin. A synchronizer is needed between the external clock and the rest of the TPM. This
synchronizer is clocked by the bus clock so the frequency of the external source must be less than one-half
the frequency of the bus rate clock. The upper frequency limit for this external clock source is specified to
be one-fourth the bus frequency to conservatively accommodate duty cycle and phase-locked loop (PLL)
or frequency-locked loop (FLL) frequency jitter effects.
On some devices the external clock input is shared with one of the TPM channels. When a TPM channel
is shared as the external clock input, the associated TPM channel cannot use the pin. (The channel can still
be used in output compare mode as a software timer.) Also, if one of the TPM channels is used as the
external clock input, the corresponding ELSnB:ELSnA control bits must be set to 0:0 so the channel is not
trying to use the same pin.
13.2.2
TPMxCHn — TPMx Channel n I/O Pins
Each TPM channel is associated with an I/O pin on the MCU. The function of this pin depends on the
configuration of the channel. In some cases, no pin function is needed so the pin reverts to being controlled
by general-purpose I/O controls. When a timer has control of a port pin, the port data and data direction
registers do not affect the related pin(s). See the Pins and Connections chapter for additional information
about shared pin functions.
13.3
Register Definition
The TPM includes:
• An 8-bit status and control register (TPMxSC)
• A 16-bit counter (TPMxCNTH:TPMxCNTL)
• A 16-bit modulo register (TPMxMODH:TPMxMODL)
Each timer channel has:
• An 8-bit status and control register (TPMxCnSC)
• A 16-bit channel value register (TPMxCnVH:TPMxCnVL)
Refer to the direct-page register summary in the Memory chapter of this data sheet for the absolute address
assignments for all TPM registers. This section refers to registers and control bits only by their names. A
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Timer/Pulse-Width Modulator (S08TPMV2)
Freescale-provided equate or header file is used to translate these names into the appropriate absolute
addresses.
13.3.1
Timer Status and Control Register (TPMxSC)
TPMxSC contains the overflow status flag and control bits that are used to configure the interrupt enable,
TPM configuration, clock source, and prescale divisor. These controls relate to all channels within this
timer module.
7
R
6
5
4
3
2
1
0
TOIE
CPWMS
CLKSB
CLKSA
PS2
PS1
PS0
0
0
0
0
0
0
0
TOF
W
Reset
0
= Unimplemented or Reserved
Figure 13-3. Timer Status and Control Register (TPMxSC)
Table 13-1. TPMxSC Register Field Descriptions
Field
Description
7
TOF
Timer Overflow Flag — This flag is set when the TPM counter changes to 0x0000 after reaching the modulo
value programmed in the TPM counter modulo registers. When the TPM is configured for CPWM, TOF is set after
the counter has reached the value in the modulo register, at the transition to the next lower count value. Clear
TOF by reading the TPM status and control register when TOF is set and then writing a 0 to TOF. If another TPM
overflow occurs before the clearing sequence is complete, the sequence is reset so TOF would remain set after
the clear sequence was completed for the earlier TOF. Reset clears TOF. Writing a 1 to TOF has no effect.
0 TPM counter has not reached modulo value or overflow
1 TPM counter has overflowed
6
TOIE
Timer Overflow Interrupt Enable — This read/write bit enables TPM overflow interrupts. If TOIE is set, an
interrupt is generated when TOF equals 1. Reset clears TOIE.
0 TOF interrupts inhibited (use software polling)
1 TOF interrupts enabled
5
CPWMS
Center-Aligned PWM Select — This read/write bit selects CPWM operating mode. Reset clears this bit so the
TPM operates in up-counting mode for input capture, output compare, and edge-aligned PWM functions. Setting
CPWMS reconfigures the TPM to operate in up-/down-counting mode for CPWM functions. Reset clears
CPWMS.
0 All TPMx channels operate as input capture, output compare, or edge-aligned PWM mode as selected by the
MSnB:MSnA control bits in each channel’s status and control register
1 All TPMx channels operate in center-aligned PWM mode
4:3
CLKS[B:A]
Clock Source Select — As shown in Table 13-2, this 2-bit field is used to disable the TPM system or select one
of three clock sources to drive the counter prescaler. The external source and the XCLK are synchronized to the
bus clock by an on-chip synchronization circuit.
2:0
PS[2:0]
Prescale Divisor Select — This 3-bit field selects one of eight divisors for the TPM clock input as shown in
Table 13-3. This prescaler is located after any clock source synchronization or clock source selection, so it affects
whatever clock source is selected to drive the TPM system.
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Table 13-2. TPM Clock Source Selection
CLKSB:CLKSA
TPM Clock Source to Prescaler Input
0:0
No clock selected (TPMx disabled)
0:1
Bus rate clock (BUSCLK)
1:0
Fixed system clock (XCLK)
1:1
External source (TPMxCLK)1,2
1
The maximum frequency that is allowed as an external clock is one-fourth of the bus
frequency.
2
If the external clock input is shared with channel n and is selected as the TPM clock source,
the corresponding ELSnB:ELSnA control bits should be set to 0:0 so channel n does not try
to use the same pin for a conflicting function.
Table 13-3. Prescale Divisor Selection
13.3.2
PS2:PS1:PS0
TPM Clock Source Divided-By
0:0:0
1
0:0:1
2
0:1:0
4
0:1:1
8
1:0:0
16
1:0:1
32
1:1:0
64
1:1:1
128
Timer Counter Registers (TPMxCNTH:TPMxCNTL)
The two read-only TPM counter registers contain the high and low bytes of the value in the TPM counter.
Reading either byte (TPMxCNTH or TPMxCNTL) latches the contents of both bytes into a buffer where
they remain latched until the other byte is read. This allows coherent 16-bit reads in either order. The
coherency mechanism is automatically restarted by an MCU reset, a write of any value to TPMxCNTH or
TPMxCNTL, or any write to the timer status/control register (TPMxSC).
Reset clears the TPM counter registers.
R
7
6
5
4
3
2
1
0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
W
Reset
Any write to TPMxCNTH clears the 16-bit counter.
0
0
0
0
0
0
Figure 13-4. Timer Counter Register High (TPMxCNTH)
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R
7
6
5
4
3
2
1
0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
W
Reset
Any write to TPMxCNTL clears the 16-bit counter.
0
0
0
0
0
0
Figure 13-5. Timer Counter Register Low (TPMxCNTL)
When background mode is active, the timer counter and the coherency mechanism are frozen such that the
buffer latches remain in the state they were in when the background mode became active even if one or
both bytes of the counter are read while background mode is active.
13.3.3
Timer Counter Modulo Registers (TPMxMODH:TPMxMODL)
The read/write TPM modulo registers contain the modulo value for the TPM counter. After the TPM
counter reaches the modulo value, the TPM counter resumes counting from 0x0000 at the next clock
(CPWMS = 0) or starts counting down (CPWMS = 1), and the overflow flag (TOF) becomes set. Writing
to TPMxMODH or TPMxMODL inhibits TOF and overflow interrupts until the other byte is written.
Reset sets the TPM counter modulo registers to 0x0000, which results in a free-running timer counter
(modulo disabled).
7
6
5
4
3
2
1
0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
R
W
Reset
Figure 13-6. Timer Counter Modulo Register High (TPMxMODH)
7
6
5
4
3
2
1
0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
R
W
Reset
Figure 13-7. Timer Counter Modulo Register Low (TPMxMODL)
It is good practice to wait for an overflow interrupt so both bytes of the modulo register can be written well
before a new overflow. An alternative approach is to reset the TPM counter before writing to the TPM
modulo registers to avoid confusion about when the first counter overflow will occur.
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13.3.4
Timer Channel n Status and Control Register (TPMxCnSC)
TPMxCnSC contains the channel interrupt status flag and control bits that are used to configure the
interrupt enable, channel configuration, and pin function.
7
6
5
4
3
2
CHnF
CHnIE
MSnB
MSnA
ELSnB
ELSnA
0
0
0
0
0
0
R
1
0
0
0
0
0
W
Reset
= Unimplemented or Reserved
Figure 13-8. Timer Channel n Status and Control Register (TPMxCnSC)
Table 13-4. TPMxCnSC Register Field Descriptions
Field
Description
7
CHnF
Channel n Flag — When channel n is configured for input capture, this flag bit is set when an active edge occurs
on the channel n pin. When channel n is an output compare or edge-aligned PWM channel, CHnF is set when
the value in the TPM counter registers matches the value in the TPM channel n value registers. This flag is
seldom used with center-aligned PWMs because it is set every time the counter matches the channel value
register, which correspond to both edges of the active duty cycle period.
A corresponding interrupt is requested when CHnF is set and interrupts are enabled (CHnIE = 1). Clear CHnF
by reading TPMxCnSC while CHnF is set and then writing a 0 to CHnF. If another interrupt request occurs before
the clearing sequence is complete, the sequence is reset so CHnF would remain set after the clear sequence
was completed for the earlier CHnF. This is done so a CHnF interrupt request cannot be lost by clearing a
previous CHnF. Reset clears CHnF. Writing a 1 to CHnF has no effect.
0 No input capture or output compare event occurred on channel n
1 Input capture or output compare event occurred on channel n
6
CHnIE
Channel n Interrupt Enable — This read/write bit enables interrupts from channel n. Reset clears CHnIE.
0 Channel n interrupt requests disabled (use software polling)
1 Channel n interrupt requests enabled
5
MSnB
Mode Select B for TPM Channel n — When CPWMS = 0, MSnB = 1 configures TPM channel n for
edge-aligned PWM mode. For a summary of channel mode and setup controls, refer to Table 13-5.
4
MSnA
Mode Select A for TPM Channel n — When CPWMS = 0 and MSnB = 0, MSnA configures TPM channel n for
input capture mode or output compare mode. Refer to Table 13-5 for a summary of channel mode and setup
controls.
3:2
ELSn[B:A]
Edge/Level Select Bits — Depending on the operating mode for the timer channel as set by
CPWMS:MSnB:MSnA and shown in Table 13-5, these bits select the polarity of the input edge that triggers an
input capture event, select the level that will be driven in response to an output compare match, or select the
polarity of the PWM output.
Setting ELSnB:ELSnA to 0:0 configures the related timer pin as a general-purpose I/O pin unrelated to any timer
channel functions. This function is typically used to temporarily disable an input capture channel or to make the
timer pin available as a general-purpose I/O pin when the associated timer channel is set up as a software timer
that does not require the use of a pin.
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Table 13-5. Mode, Edge, and Level Selection
CPWMS
MSnB:MSnA
ELSnB:ELSnA
X
XX
00
0
00
01
01
Input capture
Capture on falling edge only
11
Capture on rising or falling edge
00
Output
compare
Software compare only
Toggle output on compare
10
Clear output on compare
11
Set output on compare
10
XX
Capture on rising edge only
10
Edge-aligned
PWM
X1
1
Configuration
Pin not used for TPM channel; use as an external clock for the TPM or
revert to general-purpose I/O
01
1X
Mode
10
Center-aligned
PWM
X1
High-true pulses (clear output on compare)
Low-true pulses (set output on compare)
High-true pulses (clear output on compare-up)
Low-true pulses (set output on compare-up)
If the associated port pin is not stable for at least two bus clock cycles before changing to input capture
mode, it is possible to get an unexpected indication of an edge trigger. Typically, a program would clear
status flags after changing channel configuration bits and before enabling channel interrupts or using the
status flags to avoid any unexpected behavior.
13.3.5
Timer Channel Value Registers (TPMxCnVH:TPMxCnVL)
These read/write registers contain the captured TPM counter value of the input capture function or the
output compare value for the output compare or PWM functions. The channel value registers are cleared
by reset.
7
6
5
4
3
2
1
0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
R
W
Reset
Figure 13-9. Timer Channel Value Register High (TPMxCnVH)
7
6
5
4
3
2
1
0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
R
W
Reset
Figure 13-10. Timer Channel Value Register Low (TPMxCnVL)
In input capture mode, reading either byte (TPMxCnVH or TPMxCnVL) latches the contents of both bytes
into a buffer where they remain latched until the other byte is read. This latching mechanism also resets
(becomes unlatched) when the TPMxCnSC register is written.
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In output compare or PWM modes, writing to either byte (TPMxCnVH or TPMxCnVL) latches the value
into a buffer. When both bytes have been written, they are transferred as a coherent 16-bit value into the
timer channel value registers. This latching mechanism may be manually reset by writing to the
TPMxCnSC register.
This latching mechanism allows coherent 16-bit writes in either order, which is friendly to various
compiler implementations.
13.4
Functional Description
All TPM functions are associated with a main 16-bit counter that allows flexible selection of the clock
source and prescale divisor. A 16-bit modulo register also is associated with the main 16-bit counter in the
TPM. Each TPM channel is optionally associated with an MCU pin and a maskable interrupt function.
The TPM has center-aligned PWM capabilities controlled by the CPWMS control bit in TPMxSC. When
CPWMS is set to 1, timer counter TPMxCNT changes to an up-/down-counter and all channels in the
associated TPM act as center-aligned PWM channels. When CPWMS = 0, each channel can
independently be configured to operate in input capture, output compare, or buffered edge-aligned PWM
mode.
The following sections describe the main 16-bit counter and each of the timer operating modes (input
capture, output compare, edge-aligned PWM, and center-aligned PWM). Because details of pin operation
and interrupt activity depend on the operating mode, these topics are covered in the associated mode
sections.
13.4.1
Counter
All timer functions are based on the main 16-bit counter (TPMxCNTH:TPMxCNTL). This section
discusses selection of the clock source, up-counting vs. up-/down-counting, end-of-count overflow, and
manual counter reset.
After any MCU reset, CLKSB:CLKSA = 0:0 so no clock source is selected and the TPM is inactive.
Normally, CLKSB:CLKSA would be set to 0:1 so the bus clock drives the timer counter. The clock source
for the TPM can be selected to be off, the bus clock (BUSCLK), the fixed system clock (XCLK), or an
external input. The maximum frequency allowed for the external clock option is one-fourth the bus rate.
Refer to Section 13.3.1, “Timer Status and Control Register (TPMxSC)” and Table 13-2 for more
information about clock source selection.
When the microcontroller is in active background mode, the TPM temporarily suspends all counting until
the microcontroller returns to normal user operating mode. During stop mode, all TPM clocks are stopped;
therefore, the TPM is effectively disabled until clocks resume. During wait mode, the TPM continues to
operate normally.
The main 16-bit counter has two counting modes. When center-aligned PWM is selected (CPWMS = 1),
the counter operates in up-/down-counting mode. Otherwise, the counter operates as a simple up-counter.
As an up-counter, the main 16-bit counter counts from 0x0000 through its terminal count and then
continues with 0x0000. The terminal count is 0xFFFF or a modulus value in TPMxMODH:TPMxMODL.
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When center-aligned PWM operation is specified, the counter counts upward from 0x0000 through its
terminal count and then counts downward to 0x0000 where it returns to up-counting. Both 0x0000 and the
terminal count value (value in TPMxMODH:TPMxMODL) are normal length counts (one timer clock
period long).
An interrupt flag and enable are associated with the main 16-bit counter. The timer overflow flag (TOF) is
a software-accessible indication that the timer counter has overflowed. The enable signal selects between
software polling (TOIE = 0) where no hardware interrupt is generated, or interrupt-driven operation
(TOIE = 1) where a static hardware interrupt is automatically generated whenever the TOF flag is 1.
The conditions that cause TOF to become set depend on the counting mode (up or up/down). In
up-counting mode, the main 16-bit counter counts from 0x0000 through 0xFFFF and overflows to 0x0000
on the next counting clock. TOF becomes set at the transition from 0xFFFF to 0x0000. When a modulus
limit is set, TOF becomes set at the transition from the value set in the modulus register to 0x0000. When
the main 16-bit counter is operating in up-/down-counting mode, the TOF flag gets set as the counter
changes direction at the transition from the value set in the modulus register and the next lower count
value. This corresponds to the end of a PWM period. (The 0x0000 count value corresponds to the center
of a period.)
Because the HCS08 MCU is an 8-bit architecture, a coherency mechanism is built into the timer counter
for read operations. Whenever either byte of the counter is read (TPMxCNTH or TPMxCNTL), both bytes
are captured into a buffer so when the other byte is read, the value will represent the other byte of the count
at the time the first byte was read. The counter continues to count normally, but no new value can be read
from either byte until both bytes of the old count have been read.
The main timer counter can be reset manually at any time by writing any value to either byte of the timer
count TPMxCNTH or TPMxCNTL. Resetting the counter in this manner also resets the coherency
mechanism in case only one byte of the counter was read before resetting the count.
13.4.2
Channel Mode Selection
Provided CPWMS = 0 (center-aligned PWM operation is not specified), the MSnB and MSnA control bits
in the channel n status and control registers determine the basic mode of operation for the corresponding
channel. Choices include input capture, output compare, and buffered edge-aligned PWM.
13.4.2.1
Input Capture Mode
With the input capture function, the TPM can capture the time at which an external event occurs. When an
active edge occurs on the pin of an input capture channel, the TPM latches the contents of the TPM counter
into the channel value registers (TPMxCnVH:TPMxCnVL). Rising edges, falling edges, or any edge may
be chosen as the active edge that triggers an input capture.
When either byte of the 16-bit capture register is read, both bytes are latched into a buffer to support
coherent 16-bit accesses regardless of order. The coherency sequence can be manually reset by writing to
the channel status/control register (TPMxCnSC).
An input capture event sets a flag bit (CHnF) that can optionally generate a CPU interrupt request.
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13.4.2.2
Output Compare Mode
With the output compare function, the TPM can generate timed pulses with programmable position,
polarity, duration, and frequency. When the counter reaches the value in the channel value registers of an
output compare channel, the TPM can set, clear, or toggle the channel pin.
In output compare mode, values are transferred to the corresponding timer channel value registers only
after both 8-bit bytes of a 16-bit register have been written. This coherency sequence can be manually reset
by writing to the channel status/control register (TPMxCnSC).
An output compare event sets a flag bit (CHnF) that can optionally generate a CPU interrupt request.
13.4.2.3
Edge-Aligned PWM Mode
This type of PWM output uses the normal up-counting mode of the timer counter (CPWMS = 0) and can
be used when other channels in the same TPM are configured for input capture or output compare
functions. The period of this PWM signal is determined by the setting in the modulus register
(TPMxMODH:TPMxMODL). The duty cycle is determined by the setting in the timer channel value
register (TPMxCnVH:TPMxCnVL). The polarity of this PWM signal is determined by the setting in the
ELSnA control bit. Duty cycle cases of 0 percent and 100 percent are possible.
As Figure 13-11 shows, the output compare value in the TPM channel registers determines the pulse width
(duty cycle) of the PWM signal. The time between the modulus overflow and the output compare is the
pulse width. If ELSnA = 0, the counter overflow forces the PWM signal high and the output compare
forces the PWM signal low. If ELSnA = 1, the counter overflow forces the PWM signal low and the output
compare forces the PWM signal high.
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PULSE
WIDTH
TPMxC
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 13-11. PWM Period and Pulse Width (ELSnA = 0)
When the channel value register is set to 0x0000, the duty cycle is 0 percent. By setting the timer channel
value register (TPMxCnVH:TPMxCnVL) to a value greater than the modulus setting, 100% duty cycle
can be achieved. This implies that the modulus setting must be less than 0xFFFF to get 100% duty cycle.
Because the HCS08 is a family of 8-bit MCUs, the settings in the timer channel registers are buffered to
ensure coherent 16-bit updates and to avoid unexpected PWM pulse widths. Writes to either register,
TPMxCnVH or TPMxCnVL, write to buffer registers. In edge-PWM mode, values are transferred to the
corresponding timer channel registers only after both 8-bit bytes of a 16-bit register have been written and
the value in the TPMxCNTH:TPMxCNTL counter is 0x0000. (The new duty cycle does not take effect
until the next full period.)
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13.4.3
Center-Aligned PWM Mode
This type of PWM output uses the up-/down-counting mode of the timer counter (CPWMS = 1). The
output compare value in TPMxCnVH:TPMxCnVL determines the pulse width (duty cycle) of the PWM
signal and the period is determined by the value in TPMxMODH:TPMxMODL.
TPMxMODH:TPMxMODL should be kept in the range of 0x0001 to 0x7FFF because values outside this
range can produce ambiguous results. ELSnA will determine the polarity of the CPWM output.
pulse width = 2 x (TPMxCnVH:TPMxCnVL)
Eqn. 13-1
period = 2 x (TPMxMODH:TPMxMODL);
for TPMxMODH:TPMxMODL = 0x0001–0x7FFF
Eqn. 13-2
If the channel value register TPMxCnVH:TPMxCnVL is zero or negative (bit 15 set), the duty cycle will
be 0%. If TPMxCnVH:TPMxCnVL is a positive value (bit 15 clear) and is greater than the (nonzero)
modulus setting, the duty cycle will be 100% because the duty cycle compare will never occur. This
implies the usable range of periods set by the modulus register is 0x0001 through 0x7FFE (0x7FFF if
generation of 100% duty cycle is not necessary). This is not a significant limitation because the resulting
period is much longer than required for normal applications.
TPMxMODH:TPMxMODL = 0x0000 is a special case that should not be used with center-aligned PWM
mode. When CPWMS = 0, this case corresponds to the counter running free from 0x0000 through 0xFFFF,
but when CPWMS = 1 the counter needs a valid match to the modulus register somewhere other than at
0x0000 in order to change directions from up-counting to down-counting.
Figure 13-12 shows the output compare value in the TPM channel registers (multiplied by 2), which
determines the pulse width (duty cycle) of the CPWM signal. If ELSnA = 0, the compare match while
counting up forces the CPWM output signal low and a compare match while counting down forces the
output high. The counter counts up until it reaches the modulo setting in TPMxMODH:TPMxMODL, then
counts down until it reaches zero. This sets the period equal to two times TPMxMODH:TPMxMODL.
COUNT =
TPMxMODH:TPMx
OUTPUT
COMPARE
(COUNT DOWN)
COUNT = 0
OUTPUT
COMPARE
(COUNT UP)
COUNT =
TPMxMODH:TPMx
TPM1C
PULSE WIDTH
2x
2x
PERIOD
Figure 13-12. CPWM Period and Pulse Width (ELSnA = 0)
Center-aligned PWM outputs typically produce less noise than edge-aligned PWMs because fewer I/O pin
transitions are lined up at the same system clock edge. This type of PWM is also required for some types
of motor drives.
Because the HCS08 is a family of 8-bit MCUs, the settings in the timer channel registers are buffered to
ensure coherent 16-bit updates and to avoid unexpected PWM pulse widths. Writes to any of the registers,
TPMxMODH, TPMxMODL, TPMxCnVH, and TPMxCnVL, actually write to buffer registers. Values are
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transferred to the corresponding timer channel registers only after both 8-bit bytes of a 16-bit register have
been written and the timer counter overflows (reverses direction from up-counting to down-counting at the
end of the terminal count in the modulus register). This TPMxCNT overflow requirement only applies to
PWM channels, not output compares.
Optionally, when TPMxCNTH:TPMxCNTL = TPMxMODH:TPMxMODL, the TPM can generate a TOF
interrupt at the end of this count. The user can choose to reload any number of the PWM buffers, and they
will all update simultaneously at the start of a new period.
Writing to TPMxSC cancels any values written to TPMxMODH and/or TPMxMODL and resets the
coherency mechanism for the modulo registers. Writing to TPMxCnSC cancels any values written to the
channel value registers and resets the coherency mechanism for TPMxCnVH:TPMxCnVL.
13.5
TPM Interrupts
The TPM generates an optional interrupt for the main counter overflow and an interrupt for each channel.
The meaning of channel interrupts depends on the mode of operation for each channel. If the channel is
configured for input capture, the interrupt flag is set each time the selected input capture edge is
recognized. If the channel is configured for output compare or PWM modes, the interrupt flag is set each
time the main timer counter matches the value in the 16-bit channel value register. See the Resets,
Interrupts, and System Configuration chapter for absolute interrupt vector addresses, priority, and local
interrupt mask control bits.
For each interrupt source in the TPM, a flag bit is set on recognition of the interrupt condition such as timer
overflow, channel input capture, or output compare events. This flag may be read (polled) by software to
verify that the action has occurred, or an associated enable bit (TOIE or CHnIE) can be set to enable
hardware interrupt generation. While the interrupt enable bit is set, a static interrupt will be generated
whenever the associated interrupt flag equals 1. It is the responsibility of user software to perform a
sequence of steps to clear the interrupt flag before returning from the interrupt service routine.
13.5.1
Clearing Timer Interrupt Flags
TPM interrupt flags are cleared by a 2-step process that includes a read of the flag bit while it is set (1)
followed by a write of 0 to the bit. If a new event is detected between these two steps, the sequence is reset
and the interrupt flag remains set after the second step to avoid the possibility of missing the new event.
13.5.2
Timer Overflow Interrupt Description
The conditions that cause TOF to become set depend on the counting mode (up or up/down). In
up-counting mode, the 16-bit timer counter counts from 0x0000 through 0xFFFF and overflows to 0x0000
on the next counting clock. TOF becomes set at the transition from 0xFFFF to 0x0000. When a modulus
limit is set, TOF becomes set at the transition from the value set in the modulus register to 0x0000. When
the counter is operating in up-/down-counting mode, the TOF flag gets set as the counter changes direction
at the transition from the value set in the modulus register and the next lower count value. This corresponds
to the end of a PWM period. (The 0x0000 count value corresponds to the center of a period.)
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13.5.3
Channel Event Interrupt Description
The meaning of channel interrupts depends on the current mode of the channel (input capture, output
compare, edge-aligned PWM, or center-aligned PWM).
When a channel is configured as an input capture channel, the ELSnB:ELSnA control bits select rising
edges, falling edges, any edge, or no edge (off) as the edge that triggers an input capture event. When the
selected edge is detected, the interrupt flag is set. The flag is cleared by the 2-step sequence described in
Section 13.5.1, “Clearing Timer Interrupt Flags.”
When a channel is configured as an output compare channel, the interrupt flag is set each time the main
timer counter matches the 16-bit value in the channel value register. The flag is cleared by the 2-step
sequence described in Section 13.5.1, “Clearing Timer Interrupt Flags.”
13.5.4
PWM End-of-Duty-Cycle Events
For channels that are configured for PWM operation, there are two possibilities:
• When the channel is configured for edge-aligned PWM, the channel flag is set when the timer
counter matches the channel value register that marks the end of the active duty cycle period.
• When the channel is configured for center-aligned PWM, the timer count matches the channel
value register twice during each PWM cycle. In this CPWM case, the channel flag is set at the start
and at the end of the active duty cycle, which are the times when the timer counter matches the
channel value register.
The flag is cleared by the 2-step sequence described in Section 13.5.1, “Clearing Timer Interrupt Flags.”
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Chapter 14
Development Support
14.1
Introduction
Development support systems in the HCS08 include the background debug controller (BDC) and the
on-chip debug module (DBG). The BDC provides a single-wire debug interface to the target MCU that
provides a convenient interface for programming the on-chip FLASH and other nonvolatile memories. The
BDC is also the primary debug interface for development and allows non-intrusive access to memory data
and traditional debug features such as CPU register modify, breakpoints, and single instruction trace
commands.
In the HCS08 Family, address and data bus signals are not available on external pins. Debug is done
through commands fed into the target MCU via the single-wire background debug interface. The debug
module provides a means to selectively trigger and capture bus information so an external development
system can reconstruct what happened inside the MCU on a cycle-by-cycle basis without having external
access to the address and data signals.
14.1.1
Module Configuration
The alternate BDC clock source is the ICSLCLK. This clock source is selected by clearing the CLKSW
bit in the BDCSCR register. For details on ICSLCLK, see Section 11.4, “Functional Description” of the
ICS chapter.
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14.1.2
Features
Features of the BDC module include:
• Single pin for mode selection and background communications
• BDC registers are not located in the memory map
• SYNC command to determine target communications rate
• Non-intrusive commands for memory access
• Active background mode commands for CPU register access
• GO and TRACE1 commands
• BACKGROUND command can wake CPU from stop or wait modes
• One hardware address breakpoint built into BDC
• Oscillator runs in stop mode, if BDC enabled
• COP watchdog disabled while in active background mode
Features of the ICE system include:
• Two trigger comparators: Two address + read/write (R/W) or one full address + data + R/W
• Flexible 8-word by 16-bit FIFO (first-in, first-out) buffer for capture information:
— Change-of-flow addresses or
— Event-only data
• Two types of breakpoints:
— Tag breakpoints for instruction opcodes
— Force breakpoints for any address access
• Nine trigger modes:
— Basic: A-only, A OR B
— Sequence: A then B
— Full: A AND B data, A AND NOT B data
— Event (store data): Event-only B, A then event-only B
— Range: Inside range (A ≤ address ≤ B), outside range (address < A or address > B)
14.2
Background Debug Controller (BDC)
All MCUs in the HCS08 Family contain a single-wire background debug interface that supports in-circuit
programming of on-chip nonvolatile memory and sophisticated non-intrusive debug capabilities. Unlike
debug interfaces on earlier 8-bit MCUs, this system does not interfere with normal application resources.
It does not use any user memory or locations in the memory map and does not share any on-chip
peripherals.
BDC commands are divided into two groups:
• Active background mode commands require that the target MCU is in active background mode (the
user program is not running). Active background mode commands allow the CPU registers to be
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•
read or written, and allow the user to trace one user instruction at a time, or GO to the user program
from active background mode.
Non-intrusive commands can be executed at any time even while the user’s program is running.
Non-intrusive commands allow a user to read or write MCU memory locations or access status and
control registers within the background debug controller.
Typically, a relatively simple interface pod is used to translate commands from a host computer into
commands for the custom serial interface to the single-wire background debug system. Depending on the
development tool vendor, this interface pod may use a standard RS-232 serial port, a parallel printer port,
or some other type of communications such as a universal serial bus (USB) to communicate between the
host PC and the pod. The pod typically connects to the target system with ground, the BKGD pin, RESET,
and sometimes VDD. An open-drain connection to reset allows the host to force a target system reset,
which is useful to regain control of a lost target system or to control startup of a target system before the
on-chip nonvolatile memory has been programmed. Sometimes VDD can be used to allow the pod to use
power from the target system to avoid the need for a separate power supply. However, if the pod is powered
separately, it can be connected to a running target system without forcing a target system reset or otherwise
disturbing the running application program.
BKGD 1
2 GND
NO CONNECT 3
4 RESET
NO CONNECT 5
6 VDD
Figure 14-1. BDM Tool Connector
14.2.1
BKGD Pin Description
BKGD is the single-wire background debug interface pin. The primary function of this pin is for
bidirectional serial communication of active background mode commands and data. During reset, this pin
is used to select between starting in active background mode or starting the user’s application program.
This pin is also used to request a timed sync response pulse to allow a host development tool to determine
the correct clock frequency for background debug serial communications.
BDC serial communications use a custom serial protocol first introduced on the M68HC12 Family of
microcontrollers. This protocol assumes the host knows the communication clock rate that is determined
by the target BDC clock rate. All communication is initiated and controlled by the host that drives a
high-to-low edge to signal the beginning of each bit time. Commands and data are sent most significant
bit first (MSB first). For a detailed description of the communications protocol, refer to Section 14.2.2,
“Communication Details.”
If a host is attempting to communicate with a target MCU that has an unknown BDC clock rate, a SYNC
command may be sent to the target MCU to request a timed sync response signal from which the host can
determine the correct communication speed.
BKGD is a pseudo-open-drain pin and there is an on-chip pullup so no external pullup resistor is required.
Unlike typical open-drain pins, the external RC time constant on this pin, which is influenced by external
capacitance, plays almost no role in signal rise time. The custom protocol provides for brief, actively
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driven speedup pulses to force rapid rise times on this pin without risking harmful drive level conflicts.
Refer to Section 14.2.2, “Communication Details,” for more detail.
When no debugger pod is connected to the 6-pin BDM interface connector, the internal pullup on BKGD
chooses normal operating mode. When a debug pod is connected to BKGD it is possible to force the MCU
into active background mode after reset. The specific conditions for forcing active background depend
upon the HCS08 derivative (refer to the introduction to this Development Support section). It is not
necessary to reset the target MCU to communicate with it through the background debug interface.
14.2.2
Communication Details
The BDC serial interface requires the external controller to generate a falling edge on the BKGD pin to
indicate the start of each bit time. The external controller provides this falling edge whether data is
transmitted or received.
BKGD is a pseudo-open-drain pin that can be driven either by an external controller or by the MCU. Data
is transferred MSB first at 16 BDC clock cycles per bit (nominal speed). The interface times out if
512 BDC clock cycles occur between falling edges from the host. Any BDC command that was in progress
when this timeout occurs is aborted without affecting the memory or operating mode of the target MCU
system.
The custom serial protocol requires the debug pod to know the target BDC communication clock speed.
The clock switch (CLKSW) control bit in the BDC status and control register allows the user to select the
BDC clock source. The BDC clock source can either be the bus or the alternate BDC clock source.
The BKGD pin can receive a high or low level or transmit a high or low level. The following diagrams
show timing for each of these cases. Interface timing is synchronous to clocks in the target BDC, but
asynchronous to the external host. The internal BDC clock signal is shown for reference in counting
cycles.
Figure 14-2 shows an external host transmitting a logic 1 or 0 to the BKGD pin of a target HCS08 MCU.
The host is asynchronous to the target so there is a 0-to-1 cycle delay from the host-generated falling edge
to where the target perceives the beginning of the bit time. Ten target BDC clock cycles later, the target
senses the bit level on the BKGD pin. Typically, the host actively drives the pseudo-open-drain BKGD pin
during host-to-target transmissions to speed up rising edges. Because the target does not drive the BKGD
pin during the host-to-target transmission period, there is no need to treat the line as an open-drain signal
during this period.
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BDC CLOCK
(TARGET MCU)
HOST
TRANSMIT 1
HOST
TRANSMIT 0
10 CYCLES
SYNCHRONIZATION
UNCERTAINTY
EARLIEST START
OF NEXT BIT
TARGET SENSES BIT LEVEL
PERCEIVED START
OF BIT TIME
Figure 14-2. BDC Host-to-Target Serial Bit Timing
Figure 14-3 shows the host receiving a logic 1 from the target HCS08 MCU. Because the host is
asynchronous to the target MCU, there is a 0-to-1 cycle delay from the host-generated falling edge on
BKGD to the perceived start of the bit time in the target MCU. The host holds the BKGD pin low long
enough for the target to recognize it (at least two target BDC cycles). The host must release the low drive
before the target MCU drives a brief active-high speedup pulse seven cycles after the perceived start of the
bit time. The host should sample the bit level about 10 cycles after it started the bit time.
BDC CLOCK
(TARGET MCU)
HOST DRIVE
TO BKGD PIN
TARGET MCU
SPEEDUP PULSE
HIGH-IMPEDANCE
HIGH-IMPEDANCE
HIGH-IMPEDANCE
PERCEIVED START
OF BIT TIME
R-C RISE
BKGD PIN
10 CYCLES
10 CYCLES
EARLIEST START
OF NEXT BIT
HOST SAMPLES BKGD PIN
Figure 14-3. BDC Target-to-Host Serial Bit Timing (Logic 1)
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Figure 14-4 shows the host receiving a logic 0 from the target HCS08 MCU. Because the host is
asynchronous to the target MCU, there is a 0-to-1 cycle delay from the host-generated falling edge on
BKGD to the start of the bit time as perceived by the target MCU. The host initiates the bit time but the
target HCS08 finishes it. Because the target wants the host to receive a logic 0, it drives the BKGD pin low
for 13 BDC clock cycles, then briefly drives it high to speed up the rising edge. The host samples the bit
level about 10 cycles after starting the bit time.
BDC CLOCK
(TARGET MCU)
HOST DRIVE
TO BKGD PIN
HIGH-IMPEDANCE
SPEEDUP
PULSE
TARGET MCU
DRIVE AND
SPEED-UP PULSE
PERCEIVED START
OF BIT TIME
BKGD PIN
10 CYCLES
10 CYCLES
EARLIEST START
OF NEXT BIT
HOST SAMPLES BKGD PIN
Figure 14-4. BDM Target-to-Host Serial Bit Timing (Logic 0)
14.2.3
BDC Commands
BDC commands are sent serially from a host computer to the BKGD pin of the target HCS08 MCU. All
commands and data are sent MSB-first using a custom BDC communications protocol. Active background
mode commands require that the target MCU is currently in the active background mode while
non-intrusive commands may be issued at any time whether the target MCU is in active background mode
or running a user application program.
Table 14-1 shows all HCS08 BDC commands, a shorthand description of their coding structure, and the
meaning of each command.
Coding Structure Nomenclature
This nomenclature is used in Table 14-1 to describe the coding structure of the BDC commands.
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/
d
AAAA
RD
WD
RD16
WD16
SS
CC
RBKP
=
=
=
=
=
=
=
=
=
=
WBKP
=
Commands begin with an 8-bit hexadecimal command code in the host-to-target
direction (most significant bit first)
separates parts of the command
delay 16 target BDC clock cycles
a 16-bit address in the host-to-target direction
8 bits of read data in the target-to-host direction
8 bits of write data in the host-to-target direction
16 bits of read data in the target-to-host direction
16 bits of write data in the host-to-target direction
the contents of BDCSCR in the target-to-host direction (STATUS)
8 bits of write data for BDCSCR in the host-to-target direction (CONTROL)
16 bits of read data in the target-to-host direction (from BDCBKPT breakpoint
register)
16 bits of write data in the host-to-target direction (for BDCBKPT breakpoint register)
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Table 14-1. BDC Command Summary
Command
Mnemonic
1
Active BDM/
Non-intrusive
Coding
Structure
Description
SYNC
Non-intrusive
n/a1
Request a timed reference pulse to determine
target BDC communication speed
ACK_ENABLE
Non-intrusive
D5/d
Enable acknowledge protocol. Refer to
Freescale document order no. HCS08RMv1/D.
ACK_DISABLE
Non-intrusive
D6/d
Disable acknowledge protocol. Refer to
Freescale document order no. HCS08RMv1/D.
BACKGROUND
Non-intrusive
90/d
Enter active background mode if enabled
(ignore if ENBDM bit equals 0)
READ_STATUS
Non-intrusive
E4/SS
Read BDC status from BDCSCR
WRITE_CONTROL
Non-intrusive
C4/CC
Write BDC controls in BDCSCR
READ_BYTE
Non-intrusive
E0/AAAA/d/RD
Read a byte from target memory
READ_BYTE_WS
Non-intrusive
E1/AAAA/d/SS/RD
Read a byte and report status
READ_LAST
Non-intrusive
E8/SS/RD
Re-read byte from address just read and report
status
WRITE_BYTE
Non-intrusive
C0/AAAA/WD/d
Write a byte to target memory
WRITE_BYTE_WS
Non-intrusive
C1/AAAA/WD/d/SS
Write a byte and report status
READ_BKPT
Non-intrusive
E2/RBKP
Read BDCBKPT breakpoint register
WRITE_BKPT
Non-intrusive
C2/WBKP
Write BDCBKPT breakpoint register
GO
Active BDM
08/d
Go to execute the user application program
starting at the address currently in the PC
TRACE1
Active BDM
10/d
Trace 1 user instruction at the address in the
PC, then return to active background mode
TAGGO
Active BDM
18/d
Same as GO but enable external tagging
(HCS08 devices have no external tagging pin)
READ_A
Active BDM
68/d/RD
Read accumulator (A)
READ_CCR
Active BDM
69/d/RD
Read condition code register (CCR)
READ_PC
Active BDM
6B/d/RD16
Read program counter (PC)
READ_HX
Active BDM
6C/d/RD16
Read H and X register pair (H:X)
READ_SP
Active BDM
6F/d/RD16
Read stack pointer (SP)
READ_NEXT
Active BDM
70/d/RD
Increment H:X by one then read memory byte
located at H:X
READ_NEXT_WS
Active BDM
71/d/SS/RD
Increment H:X by one then read memory byte
located at H:X. Report status and data.
WRITE_A
Active BDM
48/WD/d
Write accumulator (A)
WRITE_CCR
Active BDM
49/WD/d
Write condition code register (CCR)
WRITE_PC
Active BDM
4B/WD16/d
Write program counter (PC)
WRITE_HX
Active BDM
4C/WD16/d
Write H and X register pair (H:X)
WRITE_SP
Active BDM
4F/WD16/d
Write stack pointer (SP)
WRITE_NEXT
Active BDM
50/WD/d
Increment H:X by one, then write memory byte
located at H:X
WRITE_NEXT_WS
Active BDM
51/WD/d/SS
Increment H:X by one, then write memory byte
located at H:X. Also report status.
The SYNC command is a special operation that does not have a command code.
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The SYNC command is unlike other BDC commands because the host does not necessarily know the
correct communications speed to use for BDC communications until after it has analyzed the response to
the SYNC command.
To issue a SYNC command, the host:
• Drives the BKGD pin low for at least 128 cycles of the slowest possible BDC clock (The slowest
clock is normally the reference oscillator/64 or the self-clocked rate/64.)
• Drives BKGD high for a brief speedup pulse to get a fast rise time (This speedup pulse is typically
one cycle of the fastest clock in the system.)
• Removes all drive to the BKGD pin so it reverts to high impedance
• Monitors the BKGD pin for the sync response pulse
The target, upon detecting the SYNC request from the host (which is a much longer low time than would
ever occur during normal BDC communications):
• Waits for BKGD to return to a logic high
• Delays 16 cycles to allow the host to stop driving the high speedup pulse
• Drives BKGD low for 128 BDC clock cycles
• Drives a 1-cycle high speedup pulse to force a fast rise time on BKGD
• Removes all drive to the BKGD pin so it reverts to high impedance
The host measures the low time of this 128-cycle sync response pulse and determines the correct speed for
subsequent BDC communications. Typically, the host can determine the correct communication speed
within a few percent of the actual target speed and the communication protocol can easily tolerate speed
errors of several percent.
14.2.4
BDC Hardware Breakpoint
The BDC includes one relatively simple hardware breakpoint that compares the CPU address bus to a
16-bit match value in the BDCBKPT register. This breakpoint can generate a forced breakpoint or a tagged
breakpoint. A forced breakpoint causes the CPU to enter active background mode at the first instruction
boundary following any access to the breakpoint address. The tagged breakpoint causes the instruction
opcode at the breakpoint address to be tagged so that the CPU will enter active background mode rather
than executing that instruction if and when it reaches the end of the instruction queue. This implies that
tagged breakpoints can only be placed at the address of an instruction opcode while forced breakpoints can
be set at any address.
The breakpoint enable (BKPTEN) control bit in the BDC status and control register (BDCSCR) is used to
enable the breakpoint logic (BKPTEN = 1). When BKPTEN = 0, its default value after reset, the
breakpoint logic is disabled and no BDC breakpoints are requested regardless of the values in other BDC
breakpoint registers and control bits. The force/tag select (FTS) control bit in BDCSCR is used to select
forced (FTS = 1) or tagged (FTS = 0) type breakpoints.
The on-chip debug module (DBG) includes circuitry for two additional hardware breakpoints that are more
flexible than the simple breakpoint in the BDC module.
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14.3
On-Chip Debug System (DBG)
Because HCS08 devices do not have external address and data buses, the most important functions of an
in-circuit emulator have been built onto the chip with the MCU. The debug system consists of an 8-stage
FIFO that can store address or data bus information, and a flexible trigger system to decide when to capture
bus information and what information to capture. The system relies on the single-wire background debug
system to access debug control registers and to read results out of the eight stage FIFO.
The debug module includes control and status registers that are accessible in the user’s memory map.
These registers are located in the high register space to avoid using valuable direct page memory space.
Most of the debug module’s functions are used during development, and user programs rarely access any
of the control and status registers for the debug module. The one exception is that the debug system can
provide the means to implement a form of ROM patching. This topic is discussed in greater detail in
Section 14.3.6, “Hardware Breakpoints.”
14.3.1
Comparators A and B
Two 16-bit comparators (A and B) can optionally be qualified with the R/W signal and an opcode tracking
circuit. Separate control bits allow you to ignore R/W for each comparator. The opcode tracking circuitry
optionally allows you to specify that a trigger will occur only if the opcode at the specified address is
actually executed as opposed to only being read from memory into the instruction queue. The comparators
are also capable of magnitude comparisons to support the inside range and outside range trigger modes.
Comparators are disabled temporarily during all BDC accesses.
The A comparator is always associated with the 16-bit CPU address. The B comparator compares to the
CPU address or the 8-bit CPU data bus, depending on the trigger mode selected. Because the CPU data
bus is separated into a read data bus and a write data bus, the RWAEN and RWA control bits have an
additional purpose, in full address plus data comparisons they are used to decide which of these buses to
use in the comparator B data bus comparisons. If RWAEN = 1 (enabled) and RWA = 0 (write), the CPU’s
write data bus is used. Otherwise, the CPU’s read data bus is used.
The currently selected trigger mode determines what the debugger logic does when a comparator detects
a qualified match condition. A match can cause:
• Generation of a breakpoint to the CPU
• Storage of data bus values into the FIFO
• Starting to store change-of-flow addresses into the FIFO (begin type trace)
• Stopping the storage of change-of-flow addresses into the FIFO (end type trace)
14.3.2
Bus Capture Information and FIFO Operation
The usual way to use the FIFO is to setup the trigger mode and other control options, then arm the
debugger. When the FIFO has filled or the debugger has stopped storing data into the FIFO, you would
read the information out of it in the order it was stored into the FIFO. Status bits indicate the number of
words of valid information that are in the FIFO as data is stored into it. If a trace run is manually halted by
writing 0 to ARM before the FIFO is full (CNT = 1:0:0:0), the information is shifted by one position and
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the host must perform ((8 – CNT) – 1) dummy reads of the FIFO to advance it to the first significant entry
in the FIFO.
In most trigger modes, the information stored in the FIFO consists of 16-bit change-of-flow addresses. In
these cases, read DBGFH then DBGFL to get one coherent word of information out of the FIFO. Reading
DBGFL (the low-order byte of the FIFO data port) causes the FIFO to shift so the next word of information
is available at the FIFO data port. In the event-only trigger modes (see Section 14.3.5, “Trigger Modes”),
8-bit data information is stored into the FIFO. In these cases, the high-order half of the FIFO (DBGFH) is
not used and data is read out of the FIFO by simply reading DBGFL. Each time DBGFL is read, the FIFO
is shifted so the next data value is available through the FIFO data port at DBGFL.
In trigger modes where the FIFO is storing change-of-flow addresses, there is a delay between CPU
addresses and the input side of the FIFO. Because of this delay, if the trigger event itself is a
change-of-flow address or a change-of-flow address appears during the next two bus cycles after a trigger
event starts the FIFO, it will not be saved into the FIFO. In the case of an end-trace, if the trigger event is
a change-of-flow, it will be saved as the last change-of-flow entry for that debug run.
The FIFO can also be used to generate a profile of executed instruction addresses when the debugger is
not armed. When ARM = 0, reading DBGFL causes the address of the most-recently fetched opcode to be
saved in the FIFO. To use the profiling feature, a host debugger would read addresses out of the FIFO by
reading DBGFH then DBGFL at regular periodic intervals. The first eight values would be discarded
because they correspond to the eight DBGFL reads needed to initially fill the FIFO. Additional periodic
reads of DBGFH and DBGFL return delayed information about executed instructions so the host debugger
can develop a profile of executed instruction addresses.
14.3.3
Change-of-Flow Information
To minimize the amount of information stored in the FIFO, only information related to instructions that
cause a change to the normal sequential execution of instructions is stored. With knowledge of the source
and object code program stored in the target system, an external debugger system can reconstruct the path
of execution through many instructions from the change-of-flow information stored in the FIFO.
For conditional branch instructions where the branch is taken (branch condition was true), the source
address is stored (the address of the conditional branch opcode). Because BRA and BRN instructions are
not conditional, these events do not cause change-of-flow information to be stored in the FIFO.
Indirect JMP and JSR instructions use the current contents of the H:X index register pair to determine the
destination address, so the debug system stores the run-time destination address for any indirect JMP or
JSR. For interrupts, RTI, or RTS, the destination address is stored in the FIFO as change-of-flow
information.
14.3.4
Tag vs. Force Breakpoints and Triggers
Tagging is a term that refers to identifying an instruction opcode as it is fetched into the instruction queue,
but not taking any other action until and unless that instruction is actually executed by the CPU. This
distinction is important because any change-of-flow from a jump, branch, subroutine call, or interrupt
causes some instructions that have been fetched into the instruction queue to be thrown away without being
executed.
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A force-type breakpoint waits for the current instruction to finish and then acts upon the breakpoint
request. The usual action in response to a breakpoint is to go to active background mode rather than
continuing to the next instruction in the user application program.
The tag vs. force terminology is used in two contexts within the debug module. The first context refers to
breakpoint requests from the debug module to the CPU. The second refers to match signals from the
comparators to the debugger control logic. When a tag-type break request is sent to the CPU, a signal is
entered into the instruction queue along with the opcode so that if/when this opcode ever executes, the
CPU will effectively replace the tagged opcode with a BGND opcode so the CPU goes to active
background mode rather than executing the tagged instruction. When the TRGSEL control bit in the DBGT
register is set to select tag-type operation, the output from comparator A or B is qualified by a block of
logic in the debug module that tracks opcodes and only produces a trigger to the debugger if the opcode at
the compare address is actually executed. There is separate opcode tracking logic for each comparator so
more than one compare event can be tracked through the instruction queue at a time.
14.3.5
Trigger Modes
The trigger mode controls the overall behavior of a debug run. The 4-bit TRG field in the DBGT register
selects one of nine trigger modes. When TRGSEL = 1 in the DBGT register, the output of the comparator
must propagate through an opcode tracking circuit before triggering FIFO actions. The BEGIN bit in
DBGT chooses whether the FIFO begins storing data when the qualified trigger is detected (begin trace),
or the FIFO stores data in a circular fashion from the time it is armed until the qualified trigger is detected
(end trigger).
A debug run is started by writing a 1 to the ARM bit in the DBGC register, which sets the ARMF flag and
clears the AF and BF flags and the CNT bits in DBGS. A begin-trace debug run ends when the FIFO gets
full. An end-trace run ends when the selected trigger event occurs. Any debug run can be stopped manually
by writing a 0 to ARM or DBGEN in DBGC.
In all trigger modes except event-only modes, the FIFO stores change-of-flow addresses. In event-only
trigger modes, the FIFO stores data in the low-order eight bits of the FIFO.
The BEGIN control bit is ignored in event-only trigger modes and all such debug runs are begin type
traces. When TRGSEL = 1 to select opcode fetch triggers, it is not necessary to use R/W in comparisons
because opcode tags would only apply to opcode fetches that are always read cycles. It would also be
unusual to specify TRGSEL = 1 while using a full mode trigger because the opcode value is normally
known at a particular address.
The following trigger mode descriptions only state the primary comparator conditions that lead to a trigger.
Either comparator can usually be further qualified with R/W by setting RWAEN (RWBEN) and the
corresponding RWA (RWB) value to be matched against R/W. The signal from the comparator with
optional R/W qualification is used to request a CPU breakpoint if BRKEN = 1 and TAG determines
whether the CPU request will be a tag request or a force request.
A-Only — Trigger when the address matches the value in comparator A
A OR B — Trigger when the address matches either the value in comparator A or the value in
comparator B
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A Then B — Trigger when the address matches the value in comparator B but only after the address for
another cycle matched the value in comparator A. There can be any number of cycles after the A match
and before the B match.
A AND B Data (Full Mode) — This is called a full mode because address, data, and R/W (optionally)
must match within the same bus cycle to cause a trigger event. Comparator A checks address, the low byte
of comparator B checks data, and R/W is checked against RWA if RWAEN = 1. The high-order half of
comparator B is not used.
In full trigger modes it is not useful to specify a tag-type CPU breakpoint (BRKEN = TAG = 1), but if you
do, the comparator B data match is ignored for the purpose of issuing the tag request to the CPU and the
CPU breakpoint is issued when the comparator A address matches.
A AND NOT B Data (Full Mode) — Address must match comparator A, data must not match the low
half of comparator B, and R/W must match RWA if RWAEN = 1. All three conditions must be met within
the same bus cycle to cause a trigger.
In full trigger modes it is not useful to specify a tag-type CPU breakpoint (BRKEN = TAG = 1), but if you
do, the comparator B data match is ignored for the purpose of issuing the tag request to the CPU and the
CPU breakpoint is issued when the comparator A address matches.
Event-Only B (Store Data) — Trigger events occur each time the address matches the value in
comparator B. Trigger events cause the data to be captured into the FIFO. The debug run ends when the
FIFO becomes full.
A Then Event-Only B (Store Data) — After the address has matched the value in comparator A, a trigger
event occurs each time the address matches the value in comparator B. Trigger events cause the data to be
captured into the FIFO. The debug run ends when the FIFO becomes full.
Inside Range (A ≤ Address ≤ B) — A trigger occurs when the address is greater than or equal to the value
in comparator A and less than or equal to the value in comparator B at the same time.
Outside Range (Address < A or Address > B) — A trigger occurs when the address is either less than
the value in comparator A or greater than the value in comparator B.
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14.3.6
Hardware Breakpoints
The BRKEN control bit in the DBGC register may be set to 1 to allow any of the trigger conditions
described in Section 14.3.5, “Trigger Modes,” to be used to generate a hardware breakpoint request to the
CPU. TAG in DBGC controls whether the breakpoint request will be treated as a tag-type breakpoint or a
force-type breakpoint. A tag breakpoint causes the current opcode to be marked as it enters the instruction
queue. If a tagged opcode reaches the end of the pipe, the CPU executes a BGND instruction to go to active
background mode rather than executing the tagged opcode. A force-type breakpoint causes the CPU to
finish the current instruction and then go to active background mode.
If the background mode has not been enabled (ENBDM = 1) by a serial WRITE_CONTROL command
through the BKGD pin, the CPU will execute an SWI instruction instead of going to active background
mode.
14.4
Register Definition
This section contains the descriptions of the BDC and DBG registers and control bits.
Refer to the high-page register summary in the device overview chapter of this data sheet for the absolute
address assignments for all DBG registers. This section refers to registers and control bits only by their
names. A Freescale-provided equate or header file is used to translate these names into the appropriate
absolute addresses.
14.4.1
BDC Registers and Control Bits
The BDC has two registers:
• The BDC status and control register (BDCSCR) is an 8-bit register containing control and status
bits for the background debug controller.
• The BDC breakpoint match register (BDCBKPT) holds a 16-bit breakpoint match address.
These registers are accessed with dedicated serial BDC commands and are not located in the memory
space of the target MCU (so they do not have addresses and cannot be accessed by user programs).
Some of the bits in the BDCSCR have write limitations; otherwise, these registers may be read or written
at any time. For example, the ENBDM control bit may not be written while the MCU is in active
background mode. (This prevents the ambiguous condition of the control bit forbidding active background
mode while the MCU is already in active background mode.) Also, the four status bits (BDMACT, WS,
WSF, and DVF) are read-only status indicators and can never be written by the WRITE_CONTROL serial
BDC command. The clock switch (CLKSW) control bit may be read or written at any time.
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14.4.1.1
BDC Status and Control Register (BDCSCR)
This register can be read or written by serial BDC commands (READ_STATUS and WRITE_CONTROL)
but is not accessible to user programs because it is not located in the normal memory map of the MCU.
7
R
6
5
4
3
BKPTEN
FTS
CLKSW
BDMACT
ENBDM
2
1
0
WS
WSF
DVF
W
Normal
Reset
0
0
0
0
0
0
0
0
Reset in
Active BDM:
1
1
0
0
1
0
0
0
= Unimplemented or Reserved
Figure 14-5. BDC Status and Control Register (BDCSCR)
Table 14-2. BDCSCR Register Field Descriptions
Field
Description
7
ENBDM
Enable BDM (Permit Active Background Mode) — Typically, this bit is written to 1 by the debug host shortly
after the beginning of a debug session or whenever the debug host resets the target and remains 1 until a normal
reset clears it.
0 BDM cannot be made active (non-intrusive commands still allowed)
1 BDM can be made active to allow active background mode commands
6
BDMACT
Background Mode Active Status — This is a read-only status bit.
0 BDM not active (user application program running)
1 BDM active and waiting for serial commands
5
BKPTEN
BDC Breakpoint Enable — If this bit is clear, the BDC breakpoint is disabled and the FTS (force tag select)
control bit and BDCBKPT match register are ignored.
0 BDC breakpoint disabled
1 BDC breakpoint enabled
4
FTS
Force/Tag Select — When FTS = 1, a breakpoint is requested whenever the CPU address bus matches the
BDCBKPT match register. When FTS = 0, a match between the CPU address bus and the BDCBKPT register
causes the fetched opcode to be tagged. If this tagged opcode ever reaches the end of the instruction queue,
the CPU enters active background mode rather than executing the tagged opcode.
0 Tag opcode at breakpoint address and enter active background mode if CPU attempts to execute that
instruction
1 Breakpoint match forces active background mode at next instruction boundary (address need not be an
opcode)
3
CLKSW
Select Source for BDC Communications Clock — CLKSW defaults to 0, which selects the alternate BDC clock
source.
0 Alternate BDC clock source
1 MCU bus clock
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Table 14-2. BDCSCR Register Field Descriptions (continued)
Field
Description
2
WS
Wait or Stop Status — When the target CPU is in wait or stop mode, most BDC commands cannot function.
However, the BACKGROUND command can be used to force the target CPU out of wait or stop and into active
background mode where all BDC commands work. Whenever the host forces the target MCU into active
background mode, the host should issue a READ_STATUS command to check that BDMACT = 1 before
attempting other BDC commands.
0 Target CPU is running user application code or in active background mode (was not in wait or stop mode when
background became active)
1 Target CPU is in wait or stop mode, or a BACKGROUND command was used to change from wait or stop to
active background mode
1
WSF
Wait or Stop Failure Status — This status bit is set if a memory access command failed due to the target CPU
executing a wait or stop instruction at or about the same time. The usual recovery strategy is to issue a
BACKGROUND command to get out of wait or stop mode into active background mode, repeat the command
that failed, then return to the user program. (Typically, the host would restore CPU registers and stack values and
re-execute the wait or stop instruction.)
0 Memory access did not conflict with a wait or stop instruction
1 Memory access command failed because the CPU entered wait or stop mode
0
DVF
Data Valid Failure Status — This status bit is not used in the MC9S08QA4 Series because it does not have any
slow access memory.
0 Memory access did not conflict with a slow memory access
1 Memory access command failed because CPU was not finished with a slow memory access
14.4.1.2
BDC Breakpoint Match Register (BDCBKPT)
This 16-bit register holds the address for the hardware breakpoint in the BDC. The BKPTEN and FTS
control bits in BDCSCR are used to enable and configure the breakpoint logic. Dedicated serial BDC
commands (READ_BKPT and WRITE_BKPT) are used to read and write the BDCBKPT register but is
not accessible to user programs because it is not located in the normal memory map of the MCU.
Breakpoints are normally set while the target MCU is in active background mode before running the user
application program. For additional information about setup and use of the hardware breakpoint logic in
the BDC, refer to Section 14.2.4, “BDC Hardware Breakpoint.”
14.4.2
System Background Debug Force Reset Register (SBDFR)
This register contains a single write-only control bit. A serial background mode command such as
WRITE_BYTE must be used to write to SBDFR. Attempts to write this register from a user program are
ignored. Reads always return 0x00.
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R
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
BDFR1
W
Reset
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
1
BDFR is writable only through serial background mode debug commands, not from user programs.
Figure 14-6. System Background Debug Force Reset Register (SBDFR)
Table 14-3. SBDFR Register Field Description
Field
Description
0
BDFR
Background Debug Force Reset — A serial active background mode command such as WRITE_BYTE allows
an external debug host to force a target system reset. Writing 1 to this bit forces an MCU reset. This bit cannot
be written from a user program.
14.4.3
DBG Registers and Control Bits
The debug module includes nine bytes of register space for three 16-bit registers and three 8-bit control
and status registers. These registers are located in the high register space of the normal memory map so
they are accessible to normal application programs. These registers are rarely if ever accessed by normal
user application programs with the possible exception of a ROM patching mechanism that uses the
breakpoint logic.
14.4.3.1
Debug Comparator A High Register (DBGCAH)
This register contains compare value bits for the high-order eight bits of comparator A. This register is
forced to 0x00 at reset and can be read at any time or written at any time unless ARM = 1.
14.4.3.2
Debug Comparator A Low Register (DBGCAL)
This register contains compare value bits for the low-order eight bits of comparator A. This register is
forced to 0x00 at reset and can be read at any time or written at any time unless ARM = 1.
14.4.3.3
Debug Comparator B High Register (DBGCBH)
This register contains compare value bits for the high-order eight bits of comparator B. This register is
forced to 0x00 at reset and can be read at any time or written at any time unless ARM = 1.
14.4.3.4
Debug Comparator B Low Register (DBGCBL)
This register contains compare value bits for the low-order eight bits of comparator B. This register is
forced to 0x00 at reset and can be read at any time or written at any time unless ARM = 1.
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14.4.3.5
Debug FIFO High Register (DBGFH)
This register provides read-only access to the high-order eight bits of the FIFO. Writes to this register have
no meaning or effect. In the event-only trigger modes, the FIFO only stores data into the low-order byte
of each FIFO word, so this register is not used and will read 0x00.
Reading DBGFH does not cause the FIFO to shift to the next word. When reading 16-bit words out of the
FIFO, read DBGFH before reading DBGFL because reading DBGFL causes the FIFO to advance to the
next word of information.
14.4.3.6
Debug FIFO Low Register (DBGFL)
This register provides read-only access to the low-order eight bits of the FIFO. Writes to this register have
no meaning or effect.
Reading DBGFL causes the FIFO to shift to the next available word of information. When the debug
module is operating in event-only modes, only 8-bit data is stored into the FIFO (high-order half of each
FIFO word is unused). When reading 8-bit words out of the FIFO, simply read DBGFL repeatedly to get
successive bytes of data from the FIFO. It isn’t necessary to read DBGFH in this case.
Do not attempt to read data from the FIFO while it is still armed (after arming but before the FIFO is filled
or ARMF is cleared) because the FIFO is prevented from advancing during reads of DBGFL. This can
interfere with normal sequencing of reads from the FIFO.
Reading DBGFL while the debugger is not armed causes the address of the most-recently fetched opcode
to be stored to the last location in the FIFO. By reading DBGFH then DBGFL periodically, external host
software can develop a profile of program execution. After eight reads from the FIFO, the ninth read will
return the information that was stored as a result of the first read. To use the profiling feature, read the FIFO
eight times without using the data to prime the sequence and then begin using the data to get a delayed
picture of what addresses were being executed. The information stored into the FIFO on reads of DBGFL
(while the FIFO is not armed) is the address of the most-recently fetched opcode.
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14.4.3.7
Debug Control Register (DBGC)
This register can be read or written at any time.
7
6
5
4
3
2
1
0
DBGEN
ARM
TAG
BRKEN
RWA
RWAEN
RWB
RWBEN
0
0
0
0
0
0
0
0
R
W
Reset
Figure 14-7. Debug Control Register (DBGC)
Table 14-4. DBGC Register Field Descriptions
Field
Description
7
DBGEN
Debug Module Enable — Used to enable the debug module. DBGEN cannot be set to 1 if the MCU is secure.
0 DBG disabled
1 DBG enabled
6
ARM
Arm Control — Controls whether the debugger is comparing and storing information in the FIFO. A write is used
to set this bit (and ARMF) and completion of a debug run automatically clears it. Any debug run can be manually
stopped by writing 0 to ARM or to DBGEN.
0 Debugger not armed
1 Debugger armed
5
TAG
Tag/Force Select — Controls whether break requests to the CPU will be tag or force type requests. If
BRKEN = 0, this bit has no meaning or effect.
0 CPU breaks requested as force type requests
1 CPU breaks requested as tag type requests
4
BRKEN
Break Enable — Controls whether a trigger event will generate a break request to the CPU. Trigger events can
cause information to be stored in the FIFO without generating a break request to the CPU. For an end trace, CPU
break requests are issued to the CPU when the comparator(s) and R/W meet the trigger requirements. For a
begin trace, CPU break requests are issued when the FIFO becomes full. TRGSEL does not affect the timing of
CPU break requests.
0 CPU break requests not enabled
1 Triggers cause a break request to the CPU
3
RWA
R/W Comparison Value for Comparator A — When RWAEN = 1, this bit determines whether a read or a write
access qualifies comparator A. When RWAEN = 0, RWA and the R/W signal do not affect comparator A.
0 Comparator A can only match on a write cycle
1 Comparator A can only match on a read cycle
2
RWAEN
Enable R/W for Comparator A — Controls whether the level of R/W is considered for a comparator A match.
0 R/W is not used in comparison A
1 R/W is used in comparison A
1
RWB
R/W Comparison Value for Comparator B — When RWBEN = 1, this bit determines whether a read or a write
access qualifies comparator B. When RWBEN = 0, RWB and the R/W signal do not affect comparator B.
0 Comparator B can match only on a write cycle
1 Comparator B can match only on a read cycle
0
RWBEN
Enable R/W for Comparator B — Controls whether the level of R/W is considered for a comparator B match.
0 R/W is not used in comparison B
1 R/W is used in comparison B
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14.4.3.8
Debug Trigger Register (DBGT)
This register can be read any time, but may be written only if ARM = 0, except bits 4 and 5 are hard-wired
to 0s.
7
6
TRGSEL
BEGIN
0
0
R
5
4
0
0
3
2
1
0
TRG3
TRG2
TRG1
TRG0
0
0
0
0
W
Reset
0
0
= Unimplemented or Reserved
Figure 14-8. Debug Trigger Register (DBGT)
Table 14-5. DBGT Register Field Descriptions
Field
Description
7
TRGSEL
Trigger Type — Controls whether the match outputs from comparators A and B are qualified with the opcode
tracking logic in the debug module. If TRGSEL is set, a match signal from comparator A or B must propagate
through the opcode tracking logic and a trigger event is only signalled to the FIFO logic if the opcode at the match
address is actually executed.
0 Trigger on access to compare address (force)
1 Trigger if opcode at compare address is executed (tag)
6
BEGIN
Begin/End Trigger Select — Controls whether the FIFO starts filling at a trigger or fills in a circular manner until
a trigger ends the capture of information. In event-only trigger modes, this bit is ignored and all debug runs are
assumed to be begin traces.
0 Data stored in FIFO until trigger (end trace)
1 Trigger initiates data storage (begin trace)
3:0
TRG[3:0]
14.4.3.9
Select Trigger Mode — Selects one of nine triggering modes, as described below.
0000 A-only
0001 A OR B
0010 A Then B
0011 Event-only B (store data)
0100 A then event-only B (store data)
0101 A AND B data (full mode)
0110 A AND NOT B data (full mode)
0111 Inside range: A ≤ address ≤ B
1000 Outside range: address < A or address > B
1001 – 1111 (No trigger)
Debug Status Register (DBGS)
This is a read-only status register.
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R
7
6
5
4
3
2
1
0
AF
BF
ARMF
0
CNT3
CNT2
CNT1
CNT0
0
0
0
0
0
0
0
0
W
Reset
= Unimplemented or Reserved
Figure 14-9. Debug Status Register (DBGS)
Table 14-6. DBGS Register Field Descriptions
Field
Description
7
AF
Trigger Match A Flag — AF is cleared at the start of a debug run and indicates whether a trigger match A
condition was met since arming.
0 Comparator A has not matched
1 Comparator A match
6
BF
Trigger Match B Flag — BF is cleared at the start of a debug run and indicates whether a trigger match B
condition was met since arming.
0 Comparator B has not matched
1 Comparator B match
5
ARMF
Arm Flag — While DBGEN = 1, this status bit is a read-only image of ARM in DBGC. This bit is set by writing 1
to the ARM control bit in DBGC (while DBGEN = 1) and is automatically cleared at the end of a debug run. A
debug run is completed when the FIFO is full (begin trace) or when a trigger event is detected (end trace). A
debug run can also be ended manually by writing 0 to ARM or DBGEN in DBGC.
0 Debugger not armed
1 Debugger armed
3:0
CNT[3:0]
FIFO Valid Count — These bits are cleared at the start of a debug run and indicate the number of words of valid
data in the FIFO at the end of a debug run. The value in CNT does not decrement as data is read out of the FIFO.
The external debug host is responsible for keeping track of the count as information is read out of the FIFO.
0000 Number of valid words in FIFO = No valid data
0001 Number of valid words in FIFO = 1
0010 Number of valid words in FIFO = 2
0011 Number of valid words in FIFO = 3
0100 Number of valid words in FIFO = 4
0101 Number of valid words in FIFO = 5
0110 Number of valid words in FIFO = 6
0111 Number of valid words in FIFO = 7
1000 Number of valid words in FIFO = 8
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MC9S08QA4
Rev. 2, 3/2008
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