XR19L400IL40-F

XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER APRIL 2018 REV. 1.0.4 GENERAL DESCRIPTION APPLICATIONS  Battery-Powered Equipment  Handheld and Mobile Devices  Handheld Terminals  Industrial Peripheral Interfaces  Point-of-Sale (POS) Systems The XR19L400 (L400) is a highly integrated device that combines a full-featured single channel Universal Asynchronous Receiver and Transmitter (UART) and RS485 transceivers. The L400 is designed to operate with a single 3.3V or 5V power supply. The L400 is fully compliant with RS-485 Standards. The L400 operates in four different modes: Active, Partial Sleep, Full Sleep and Power-Save. Each mode can be invoked via hardware or software. Upon power-up, the L400 is in the Active mode where the UART and RS-485 transceiver function normally. In the Partial Sleep mode, the internal crystal oscillator of the UART or charge pump of the RS-485 transceiver is turned off. In Full Sleep mode, both the crystal oscillator and the charge pump are turned off. While the UART is in the Sleep mode, the Power-Save mode isolates the core logic from the control signals (chip select, read/write strobes, address and data bus lines) to minimize the power consumption. The RS-485 receivers remain active in any of these four modes. FEATURES  Meets true RS-485 standards at 3.3V or 5V operation  Up to 8 Mbps data transmission rate  45us sleep mode exit (charge pump to full power)  ESD protection for RS-485 I/O pins at ■ ■ ■ +/-15kV - Human Body Model +/- 8kV - IEC 61000-4-2, Contact Discharge +/- 15kV - IEC 61000-4-2, Air-Gap Discharge  Software compatible with industry standard 16550 UART  Intel/Motorola bus select  Complete modem interface  Sleep and Power-save modes to conserve battery power  Wake-up interrupt upon exiting low power modes *5 V Tolerant Inputs HALF/FULL# UART Registers C1- C1+ ACP VCC50 R_EN VCC33 GND Crystal Osc/Buffer Intel or Motorola Bus Interface PwrSave A2:A0 D7:D0 IOR# IOW# (R/W#) CS# (CS#) INT (IRQ#) RESET (RESET#) I/M# XTAL2 XTAL1 FIGURE 1. BLOCK DIAGRAM Charge Pump BRG 64 Byte TX FIFO TX 64 Byte RX FIFO RX TX+ TXRX+ RXVCC33 CTS# Modem I/Os DSR# RI# CD# UART RS-485 Transceiver XR19L400 1 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 D0 NC RXA+ RXA- D1 D2 D3 C1+ C1NC NC D4 D5 D6 D7 31 GND 33 VCC50 32 TXA+ 34 HALF/FULL# 35 TEST0 36 TEST1 37 IRQ# 38 A2 39 A1 8 CS# 9 TEST2 10 VCC 30 TXA- 29 28 NC RXA+ RXA- 27 26 25 24 23 22 21 C1+ C1NC NC NC VCC33 R_EN 20 NC VCC33 R_EN 20 RESET 18 ACP 19 I/M# 17 NC 16 IOR# 15 IOW# 14 XTAL2 13 XTAL1 12 POWERSAVE 11 21 7 RESET# 18 ACP 19 CS# TEST2 10 XR19L400 40-pin QFN Motorola Bus Mode 4 5 6 I/M# 17 8 9 3 NC 16 25 24 23 22 1 2 NC 15 27 26 XR19L 400 40 - pin QFN Intel Bus Mode 7 TXA- 29 28 R/W# 14 4 5 6 40 A0 31 GND 33 VCC50 32 TXA+ 34 HALF/FULL# 35 TEST0 36 TEST1 37 INT 38 A2 3 30 XTAL2 13 D4 D5 D6 D7 1 2 XTAL1 12 D1 D2 D3 POWERSAVE 11 D0 39 A1 40 A0 FIGURE 2. PIN OUT OF THE DEVICE GND ORDERING INFORMATION(1) PART NUMBER OPERATING TEMPERATURE RANGE LEAD-FREE PACKAGE PACKAGING METHOD XR19L400IL40TR-F -40°C to +85°C Yes(2) 40-pin QFN Tape and Reel NOTES: 1. Refer to www.exar.com/XR19L400 for most up-to-date Ordering Information. 2. Visit www.exar.com for additional information on Environmental Rating. 2 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 PIN DESCRIPTIONS Pin Descriptions NAME 40-QFN PIN# TYPE DESCRIPTION DATA BUS INTERFACE (CMOS/TTL Voltage Levels) A2 A1 A0 38 39 40 I D7 D6 D5 D4 D3 D2 D1 D0 8 7 6 5 4 3 2 1 I/O IOR# (NC) 15 I When I/M# pin is HIGH, the Intel bus interface is selected and this input becomes read strobe (active LOW). The falling edge instigates an internal read cycle and retrieves the data byte from an internal register pointed by the address lines [A2:A0], puts the data byte on the data bus to allow the host processor to read it on the rising edge. When I/M# pin is LOW, the Motorola bus interface is selected and this input is not used. IOW# (R/W#) 14 I When I/M# pin is HIGH, it selects Intel bus interface and this input becomes write strobe (active LOW). The falling edge instigates the internal write cycle and the rising edge transfers the data byte on the data bus to an internal register pointed by the address lines. When I/M# pin is LOW, the Motorola bus interface is selected and this input becomes read (HIGH) and write (LOW) signal. CS# (CS#) 9 I This input is the chip select (active low) for the UART in both the Intel and Motorola bus modes. INT (IRQ#) 37 Address bus lines [2:0]. These 3 address lines select one of the internal registers in the UART during a data bus transaction. Data bus lines [7:0] (bidirectional). O When I/M# pin is HIGH, it selects Intel bus interface and this output become the active (OD) HIGH interrupt output. This output is enabled through the software setting of MCR[3]. This output is set to the active mode when MCR[3] is set to a logic 1, and set to the three state mode when MCR[3] is set to a logic 0. See MCR[3]. When I/M# pin is LOW, it selects Motorola bus interface and this output becomes the active LOW, open-drain interrupt output for both channels. An external pull-up resistor is required for proper operation. MCR[3] must be set to a logic 0 for proper operation of the interrupt. SERIAL I/O INTERFACE (RS-485/RS-485 Voltage Levels) TX+ TX- 32 30 O Differential UART Transmit Data. RX+ RX- 28 27 I Differential UART Receive Data. ANCILLARY SIGNALS (CMOS/TTL Voltage Levels) HALF/ FULL# 34 I Half-duplex or full-duplex mode select. This pin is sampled upon power-up. When HALF/FULL# is HIGH, half-duplex mode is enabled. When HALF/FULL# is LOW, full-duplex mode is enabled. After power-up, FCTR bit-3 can select between the half-duplex or full-duplex modes. XTAL1 12 I Crystal or external clock input. 3 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 Pin Descriptions NAME 40-QFN PIN# TYPE XTAL2 13 O Crystal or buffered clock output. PwrSave 11 I Power-Save (active high). This feature isolates the L400’s data bus interface from the host preventing other bus activities that cause higher power drain during sleep mode. ACP 19 I Autosleep for Charge Pump (active HIGH). When the power supply is 3.3V, this pin shuts off the charge pump if the UART is already in sleep mode, i.e. the XTAL2 output is LOW. When the power supply is 5V, this pin should be connected to GND. I/M# 17 I Intel or Motorola Bus Select. When I/M# pin is HIGH, 16 or Intel Mode, the device will operate in the Intel bus type of interface. When I/M# pin is LOW, 68 or Motorola mode, the device will operate in the Motorola bus type of interface. RESET (RESET#) 18 I When I/M# pin is HIGH for Intel bus interface, this input becomes RESET (active high). When I/M# pin is LOW for Motorola bus interface, this input becomes RESET# (active low). A 40 ns minimum active pulse on this pin will reset the internal registers and all outputs of the UART. The UART transmitter output will be held HIGH, the receiver input will be ignored and outputs are reset during reset period. C1C1+ 25 26 - Charge pump capacitors. As shown in Figure 1, a 0.22 uF capacitor should be placed between these 2 pins. R_EN 20 I Regulator Enable. This pin regulates the 5V VCC down to 3.3V internally for the UART. When the supply voltage is 3.3V, connect R_EN to GND. When the supply voltage is 5V, connect R_EN to VCC. TEST0 TEST1 TEST2 35 36 10 I I I Factory Test Modes. For normal operation, these pins must be connected to GND. VCC33 21 Pwr 3.3V power supply. When VCC33 is used, R_EN pin should be connected to GND. A 0.1 uF capacitor to GND is recommended on this power supply pin. If VCC33 is not used as the power supply pin, VCC33 should be left unconnected. See Figure 3. All CMOS/ TTL input pins, except XTAL1, are 5V tolerant. VCC50 33 Pwr 5.0V power supply. When VCC50 is used, R_EN pin should be connected to VCC. A 1uF capacitor to GND is recommended on the VCC50 power supply pin. The 1uF capacitor is recommended whether VCC33 or VCC50 is used as the power supply pin. See Figure 3. All CMOS/TTL input pins, except XTAL1, are 5V tolerant. GND 31 Pwr Power supply common, ground. - PAD NC 16, 22, 23, 24, 29 DESCRIPTION Pwr The center pad on the backside of the QFN package is metallic and is not electrically connected to anything inside the device. It must be soldered on to the PCB and may be optionally connected to GND on the PCB. The thermal pad size on the PCB should be the approximate size of this center pad and should be solder mask defined. The solder mask opening should be at least 0.0025" inwards from the edge of the PCB thermal pad. - No Connect. Note that in Motorola mode, the IOR# pin also becomes an NC pin. NOTE: Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain. For CMOS/TTL Voltage levels, ’LOW’ indicates a voltage in the range 0V to VIL and ’HIGH" indicates a voltage in the range VIH to VCC. 4 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FIGURE 3. RECOMMENDED 3.3V OR 5V POWER SUPPLY CONNECTIONS 3.3V Power Supply 5V Power Supply VCC50 VCC50 5V 1 uF 1 uF GND GND 3.3V VCC33 VCC33 R_EN R_EN 0.1 uF GND GND 5 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 1.0 PRODUCT DESCRIPTION The XR19L400 consists of a single channel UART and RS-485 transceivers. It operates from a single +3.3V or 5V supply with data rates up to 8Mbps, while meeting all EIA/TIA-485 specifications. The configuration register set is 16550 UART compatible for control, status and data transfer. Also, the L400 has 64-bytes of transmit and receive FIFOs, automatic Xon/Xoff software flow control, transmit and receive FIFO trigger levels, and a programmable fractional baud rate generator with a prescaler of divide by 1 or 4. Additionally, the L400 includes the ACP pin which the user can shut down the charge pump for the RS-485 drivers (when operating at 3.3V). In the UART portion, the Power-Save feature isolates the databus interface to further reduce power consumption in the Sleep mode. The L400 is fabricated using an advanced CMOS process. Enhanced Features The L400 UART provides a solution that supports 64 bytes of transmit and receive FIFO. Increased performance is realized in the L400 by the transmit and receive FIFOs, FIFO trigger level controls and automatic flow control mechanism. This allows the external processor to handle more networking tasks within a given time. This increases the service interval giving the external CPU additional time for other applications and reducing the overall UART interrupt servicing time. In addition, the L400 provides the ACP and PowerSave modes that drastically reduces the power consumption when the device is not used. The combination of the above greatly reduces the CPU’s bandwidth requirement, increases performance, and reduces power consumption. Intel or Motorola Data Bus Interface The L400 provides a host interface that supports Intel or Motorola microprocessor (CPU) data bus interface. The Intel bus compatible interface allows direct interconnect to Intel compatible type of CPUs using IOR#, IOW# and CS# inputs for data bus operation. The Motorola bus compatible interface instead uses the R/W# and CS# signals for data bus transactions. See pin description section for details on all the control signals. The Intel and Motorola bus interface selection is made through the pin, I/M#. Data Rate The L400 is capable of operation up to 8 Mbps data rate. The device can operate either with a crystal on pins XTAL1 and XTAL2, or external clock source on XTAL1 pin. Internal Enhanced Register Sets The L400 UART has a set of enhanced registers providing control and monitoring functions. Interrupt enable/ disable and status, FIFO enable/disable, selectable TX and RX FIFO trigger levels, automatic hardware/ software flow control enable/disable, programmable baud rates, modem interface controls and status, sleep mode and infrared mode are all standard features. RS-485 Interface The L400 includes RS-485 drivers/receivers for the interface. This feature eliminates the need for an external RS-485 transceiver. The RS-485 transceiver can be selected to operate in either the half-duplex or full-duplex mode upon power-up via the HALF/FULL# pin. The RS-485 drivers guarantee a data rate of up to 8 Mbps. All RS-485 drivers and receivers are protected to ±15kV using the Human Body Model ground combination, ±8kV using IEC 61000-4-2 Contact Discharge, and ±15kV using IEC 61000-4-2 Air-Gap Discharge. For more information, send an e-mail to uarttechsupport@exar.com. 6 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 2.0 FUNCTIONAL DESCRIPTIONS 2.1 CPU Interface The CPU interface is 8 data bits wide with 3 address lines and control signals to execute data bus read and write transactions. The L400 data interface supports the Intel compatible types of CPUs and it is compatible to the industry standard 16C550 UART. No clock (oscillator nor external clock) is required to operate a data bus transaction. Each bus cycle is asynchronous using CS#, IOR# and IOW# or R/W# inputs. A typical data bus interconnection for Intel and Motorola mode is shown in Figure 4. FIGURE 4. XR19L400 TYPICAL INTEL/MOTOROLA DATA BUS INTERCONNECTIONS D0 D1 D2 D3 D4 D5 D6 D7 D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A0 A1 A2 IOR# IOW# IOR# IOW# UART_ CS# VCC3.3 VCC3.3 VCC5.0 VCC5.0 TX+ RX+ UART Channel A RS-485 Interface TXRX- CS# INT UART_ INT R_EN R_EN ACP ACP PWRSAVE GND PWRSAVE UART_ RESET RESET Intel Data Bus Interconnections D0 D1 D2 D3 D4 D5 D6 D7 D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A0 A1 A2 VCC IOR# IOW# R/W# UART_ CS # CS# VCC UART_INT VCC3.3 VCC3.3 VCC5.0 VCC5.0 TX+ RX+ UART Channel A TXRX- INT R_EN R_EN ACP ACP PWRSAVE GND PWRSAVE UART_ RESET RESET Motorola Data Bus Interconnections 7 RS-485 Interface XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER 2.2 REV. 1.0.4 5-Volt Tolerant Inputs The CMOS/TTL level inputs of the L400 can accept up to 5V inputs when operating at 3.3V. Note that the XTAL1 pin is not 5V tolerant when an external clock supply is used. 2.3 Device Hardware Reset The RESET or RESET# input resets the internal registers and the serial interface outputs in both channels to their default state (see Table 14). An active pulse of longer than 40 ns duration will be required to activate the reset function in the device. 2.4 Device Identification and Revision The XR19L400 provides a Device Identification code and a Device Revision code to distinguish the part from other devices and revisions. To read the identification code from the part, it is required to set the baud rate generator registers DLL and DLM both to 0x00. Now reading the content of the DLM will provide 0x01 and reading the content of DLL will provide the revision of the part; for example, a reading of 0x01 means revision A. 2.5 Channel Internal Registers Each UART channel in the L400 has a set of enhanced registers for control, monitoring and data loading and unloading. The configuration register set is compatible to those already available in the standard single 16C550 and dual ST16C2550. These registers function as data holding registers (THR/RHR), interrupt status and control registers (ISR/IER), a FIFO control register (FCR), receive line status and control registers (LSR/ LCR), modem status and control registers (MSR/MCR), programmable data rate (clock) divisor registers (DLL/ DLM), and an user accessible Scratchpad register (SPR). Beyond the general 16C2550 features and capabilities, the L400 offers enhanced feature registers, namely, EFR, Xon/Xoff 1, Xon/Xoff 2, FCTR, TRG, EMSR and FC that provide Xon/Xoff software flow control, FIFO trigger level control and FIFO level counters. All the register functions are discussed in full detail later in “Section 3.0, UART Internal Registers” on page 20. 2.6 INT (IRQ#) Output The interrupt output changes according to the operating mode and enhanced features setup. Table 1 and Table 2 below summarize the operating behavior for the transmitter and receiver in the Intel and Motorola modes. Also see Figures 18 through 21. TABLE 1: INT (IRQ#) PIN OPERATION FOR TRANSMITTER FCR BIT-0 = 0 (FIFO DISABLED) FCR BIT-0 = 1 (FIFO ENABLED) INT Pin (I/M# = 1) 0 = one byte in THR 1 = THR empty 0 = FIFO above trigger level 1 = FIFO below trigger level or FIFO empty IRQ# Pin (I/M# = 0) 1 = one byte in THR 0 = THR empty 1 = FIFO above trigger level 0 = FIFO below trigger level or FIFO empty TABLE 2: INT (IRQ#) PIN OPERATION FOR RECEIVER FCR BIT-0 = 1 (FIFO ENABLED) FCR BIT-0 = 0 (FIFO DISABLED) INT Pin (I/M# = 1) 0 = no data 1 = 1 byte 0 = FIFO below trigger level 1 = FIFO above trigger level IRQ# Pin (I/M# = 0) 1 = no data 0 = 1 byte 1 = FIFO below trigger level 0 = FIFO above trigger level 8 XR19L400 REV. 1.0.4 2.7 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER Crystal or External Clock Input The L400 includes an on-chip oscillator (XTAL1 and XTAL2) to generate a clock when a crystal is connected between the XTAL1 and XTAL2 pins of the device. Alternatively, an external clock can be supplied through the XTAL1 pin. The CPU data bus does not require this clock for bus operation. The crystal oscillator provides a system clock to the Baud Rate Generators (BRG) section found in each of the UART. XTAL1 is the input to the oscillator or external clock input and XTAL2 pin is the bufferred output which can be used as a clock signal for other devices in the system. Please note that the input XTAL1 is not 5V tolerant and therefore, the maximum voltage at the pin should be 3.3V when an external clock is supplied. For programming details, see “Programmable Baud Rate Generator.” FIGURE 5. TYPICAL CRYSTAL CONNECTIONS XTAL1 XTAL2 R2 500K - 1M Y1 C1 22-47pF R1 0-120 (Optional) 1.8432 MHz to 24 MHz C2 22-47pF The on-chip oscillator is designed to use an industry standard microprocessor crystal (parallel resonant, fundamental frequency with 10-22 pF capacitance load, ESR of 20-120 ohms and 100ppm frequency tolerance) connected externally between the XTAL1 and XTAL2 pins. When VCC = 5V, the on-chip oscillator can operate with a crystal whose frequency is not greater than 24 MHz. On the other hand, the L400 can accept an external clock of up to 64 MHz at XTAL1 pin which results in a maximum data rate of 8 Mbps. For further reading on the oscillator circuit please see DAN108 on EXAR’s web site at http://www.exar.com. 2.8 Programmable Baud Rate Generator with Fractional Divisor Each UART has its own Baud Rate Generator (BRG) with a prescaler for the transmitter and receiver. The prescaler is controlled by a software bit in the MCR register. The MCR register bit-7 sets the prescaler to divide the input crystal or external clock by 1 or 4. The output of the prescaler clocks to the BRG. The BRG further divides this clock by a programmable divisor between 1 and (216 - 0.0625) in increments of 0.0625 (1/16) to obtain a 16X or 8X sampling clock of the serial data rate. The sampling clock is used by the transmitter for data bit shifting and receiver for data sampling. The BRG divisor (DLL, DLM and DLD registers) defaults to the value of ’1’ (DLL = 0x01, DLM = 0x00 and DLD = 0x00) upon reset. Therefore, the BRG must be programmed during initialization to the operating data rate. The DLL and DLM registers provide the integer part of the divisor and the DLD register provides the fractional part of the dvisior. Only the four lower bits of the DLD are implemented and they are used to select a value from 0 (for setting 0000) to 0.9375 or 15/16 (for setting 1111). Programming the Baud Rate Generator Registers DLL, DLM and DLD provides the capability for selecting the operating data rate. Table 3 shows the standard data rates available with a 24MHz crystal or external clock at 16X clock rate. If the pre-scaler is used (MCR bit-7 = 1), the output data rate will be 4 times less than that shown in Table 3. At 8X sampling rate, these data rates would double. Also, when using 8X sampling mode, please note that the bit- 9 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 time will have a jitter (+/- 1/16) whenever the DLD is non-zero and is an odd number. When using a nonstandard data rate crystal or external clock, the divisor value can be calculated with the following equation(s): Required Divisor (decimal) = (XTAL1 clock frequency / prescaler) / (serial data rate x 16), with 16X mode EMSR[7] = 1 Required Divisor (decimal) = (XTAL1 clock frequency / prescaler / (serial data rate x 8), with 8X mode EMSR[7] = 0 The closest divisor that is obtainable in the L400 can be calculated using the following formula: ROUND( (Required Divisor - TRUNC(Required Divisor) )*16)/16 + TRUNC(Required Divisor), where DLM = TRUNC(Required Divisor) >> 8 DLL = TRUNC(Required Divisor) & 0xFF DLD = ROUND( (Required Divisor-TRUNC(Required Divisor) )*16) In the formulas above, please note that: TRUNC (N) = Integer Part of N. For example, TRUNC (5.6) = 5. ROUND (N) = N rounded towards the closest integer. For example, ROUND (7.3) = 7 and ROUND (9.9) = 10. A >> B indicates right shifting the value ’A’ by ’B’ number of bits. For example, 0x78A3 >> 8 = 0x0078. FIGURE 6. BAUD RATE GENERATOR DLL, DLM and DLD Registers Prescaler Divide by 1 XTAL1 XTAL2 Crystal Osc/ Buffer Prescaler Divide by 4 10 MCR Bit-7=0 (default) Fractional Baud Rate Generator Logic MCR Bit-7=1 16X or 8X Sampling Rate Clock to Transmitter and Receiver XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 TABLE 3: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING Required Output Data Rate DIVISOR FOR 16x Clock (Decimal) DIVISOR OBTAINABLE IN L400 DLM PROGRAM VALUE (HEX) DLL PROGRAM VALUE (HEX) DLD PROGRAM VALUE (HEX) DATA ERROR RATE (%) 400 3750 3750 E A6 0 0 2400 625 625 2 71 0 0 4800 312.5 312 8/16 1 38 8 0 9600 156.25 156 4/16 0 9C 4 0 10000 150 150 0 96 0 0 19200 78.125 78 2/16 0 4E 2 0 25000 60 60 0 3C 0 0 28800 52.0833 52 1/16 0 34 1 0.04 38400 39.0625 39 1/16 0 27 1 0 50000 30 30 0 1E 0 0 57600 26.0417 26 1/16 0 1A 1 0.08 75000 20 20 0 14 0 0 100000 15 15 0 F 0 0 115200 13.0208 13 0 D 0 0.16 153600 9.7656 9 12/16 0 9 C 0.16 200000 7.5 7 8/16 0 7 8 0 225000 6.6667 6 11/16 0 6 B 0.31 230400 6.5104 6 8/16 0 6 8 0.16 250000 6 6 0 6 0 0 300000 5 5 0 5 0 0 400000 3.75 3 12/16 0 3 C 0 460800 3.2552 3 4/16 0 3 4 0.16 500000 3 3 0 3 0 0 750000 2 2 0 2 0 0 921600 1.6276 1 10/16 0 1 A 0.16 1000000 1.5 1 8/16 0 1 8 0 11 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 C1- C1+ ACP FIGURE 7. XR19L400 TRANSMITTER AND RECEIVER Charge Pum p TX+ TX- TX UART RX+ RX RX- RS-485 Transceiver 2.9 Transmitter The transmitter section comprises of an 8-bit Transmit Shift Register (TSR) and 64 bytes of FIFO which includes a byte-wide Transmit Holding Register (THR). TSR shifts out every data bit with the 16X/8X internal clock. A bit time is 16 (8) clock periods (see EMSR bit-7). The transmitter sends the start-bit followed by the number of data bits, inserts the proper parity-bit if enabled, and adds the stop-bit(s). The status of the FIFO and TSR are reported in the Line Status Register (LSR bit-5 and bit-6). 2.9.1 Transmit Holding Register (THR) - Write Only The transmit holding register is an 8-bit register providing a data interface to the host processor. The host writes transmit data byte to the THR to be converted into a serial data stream including start-bit, data bits, parity-bit and stop-bit(s). The least-significant-bit (Bit-0) becomes first data bit to go out. The THR is the input register to the transmit FIFO of 64 bytes when FIFO operation is enabled by FCR bit-0. Every time a write operation is made to the THR, the FIFO data pointer is automatically bumped to the next sequential data location. 2.9.2 Transmitter Operation in non-FIFO Mode The host loads transmit data to THR one character at a time. The THR empty flag (LSR bit-5) is set when the data byte is transferred to TSR. THR flag can generate a transmit empty interrupt (ISR bit-1) when it is enabled by IER bit-1. The TSR flag (LSR bit-6) is set when TSR becomes completely empty. 12 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FIGURE 8. TRANSMITTER OPERATION IN NON-FIFO MODE Transmit Holding Register (THR) Data Byte 16X or 8X Clock (EMSR Bit-7) THR Interrupt (ISR bit-1) Enabled by IER bit-1 Transmit Shift Register (TSR) M S B L S B TXNOFIFO1 2.9.3 Transmitter Operation in FIFO Mode The host may fill the transmit FIFO with up to 64 bytes of transmit data. The THR empty flag (LSR bit-5) is set whenever the FIFO is empty. The THR empty flag can generate a transmit empty interrupt (ISR bit-1) when the amount of data in the FIFO falls below its programmed trigger level. The transmit empty interrupt is enabled by IER bit-1. The Transmitter Empty Flag (LSR bit-6) is set when both the TSR and the FIFO become empty. FIGURE 9. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE Transmit Data Byte Transmit FIFO THR Interrupt (ISR bit-1) falls below the programmed Trigger Level and then when becomes empty. FIFO is Enabled by FCR bit-0=1 Flow Control Characters (Xoff1/2 and Xon1/2 Reg.) Auto Software Flow Control 16X or 8X Clock (EMSR bit-7) Transmit Data Shift Register (TSR) TXFIFO1 2.10 Receiver The receiver section contains an 8-bit Receive Shift Register (RSR) and 64 bytes of FIFO which includes a byte-wide Receive Holding Register (RHR). The RSR uses the 16X/8X clock (EMSR bit-7) for timing. It verifies and validates every bit on the incoming character in the middle of each data bit. On the falling edge of a start or false start bit, an internal receiver counter starts counting at the 16X/8X clock rate. After 8 clocks (or 4 if 8X) the start bit period should be at the center of the start bit. At this time the start bit is sampled and if it is still a logic 0 it is validated. Evaluating the start bit in this manner prevents the receiver from assembling a false character. The rest of the data bits and stop bits are sampled and validated in this same manner to prevent false framing. If there were any error(s), they are reported in the LSR register bits 2-4. Upon unloading the receive data byte from RHR, the receive FIFO pointer is bumped and the error tags are immediately updated to reflect the status of the data byte in RHR register. RHR can generate a receive data ready interrupt upon receiving a character or delay until it reaches the FIFO trigger level. Furthermore, data delivery to the host is guaranteed by a receive data ready time-out interrupt when data is not received for 4 word lengths as defined by LCR[1:0] plus 12 bits time. This is equivalent to 3.7-4.6 character times. The RHR interrupt is enabled by IER bit-0. 13 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER 2.10.1 REV. 1.0.4 Receive Holding Register (RHR) - Read-Only The Receive Holding Register is an 8-bit register that holds a receive data byte from the Receive Shift Register. It provides the receive data interface to the host processor. The RHR register is part of the receive FIFO of 64 bytes by 11-bits wide, the 3 extra bits are for the 3 error tags to be reported in LSR register. When the FIFO is enabled by FCR bit-0, the RHR contains the first data character received by the FIFO. After the RHR is read, the next character byte is loaded into the RHR and the errors associated with the current data byte are immediately updated in the LSR bits 2-4. FIGURE 10. RECEIVER OPERATION IN NON-FIFO MODE 16X or 8X Clock (EMSR bit-7) Receive Data Byte and Errors Receive Data Shift Register (RSR) Error Tags in LSR bits 4:2 Receive Data Holding Register (RHR) Data Bit Validation Receive Data Characters RHR Interrupt (ISR bit-2) RXFIFO1 2.11 Auto Xon/Xoff (Software) Flow Control When software flow control is enabled (See Table 13), the L400 compares one or two sequential receive data characters with the programmed Xon or Xoff-1,2 character value(s). If receive character(s) (RX) match the programmed values, the L400 will halt transmission (TX) as soon as the current character has completed transmission. When a match occurs, the Xoff (if enabled via IER bit-5) flag will be set and the interrupt output pin will be activated. Following a suspension due to a match of the Xoff character, the L400 will monitor the receive data stream for a match to the Xon-1,2 character. If a match is found, the L400 will resume operation and clear the flags (ISR bit-4). Reset initially sets the contents of the Xon/Xoff 8-bit flow control registers to a logic 0. Following reset the user can write any Xon/Xoff value desired for software flow control. Different conditions can be set to detect Xon/ Xoff characters (See Table 13) and suspend/resume transmissions. When double 8-bit Xon/Xoff characters are selected, the L400 compares two consecutive receive characters with two software flow control 8-bit values (Xon1, Xon2, Xoff1, Xoff2) and controls TX transmissions accordingly. Under the above described flow control mechanisms, flow control characters are not placed (stacked) in the user accessible RX data buffer or FIFO. In the event that the receive buffer is overfilling and flow control needs to be executed, the L400 automatically sends an Xoff message (when enabled) via the serial TX output to the remote modem. The L400 sends the Xoff-1,2 characters two-character-times (= time taken to send two characters at the programmed baud rate) after the receive FIFO crosses the programmed trigger level (for all trigger tables A-D). To clear this condition, the L400 will transmit the programmed Xon-1,2 characters as soon as receive FIFO is less than one trigger level below the programmed trigger level (for Trigger Tables A, B, and C) or when receive FIFO is less than the 14 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 trigger level minus the hysteresis value (for Trigger Table D). These hysteresis values are shown in Table 11. Table 4 below explains this when Trigger Table-B (See Table 12) is selected. TABLE 4: AUTO XON/XOFF (SOFTWARE) FLOW CONTROL RX TRIGGER LEVEL INT PIN ACTIVATION XOFF CHARACTER(S) SENT (CHARACTERS IN RX FIFO) XON CHARACTER(S) SENT (CHARACTERS IN RX FIFO) 8 8 8* 0 16 16 16* 8 24 24 24* 16 28 28 28* 24 * After the trigger level is reached, an xoff character is sent after a short span of time (= time required to send 2 characters); for example, after 2.083ms has elapsed for 9600 baud and 8-bit word length, no parity and 1 stop bit setting. 15 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER 2.12 REV. 1.0.4 Sleep Mode, ACP Mode and Power-Save Feature with Wake-Up Interrupt 2.12.1 UART sleep mode (3.3V or 5V operation) The UART portion in the L400 can enter sleep mode if all of these conditions are satisfied: ■ no interrupts pending (ISR bit-0 = 1) ■ the 16-bit divisor programmed in DLM and DLL registers is a non-zero value ■ sleep mode is enabled (IER bit-4 = 1) ■ modem inputs are not toggling (MSR bits 0-3 = 0) ■ RX input pins are idle The L400 stops its crystal oscillator to conserve power in this mode. The user can check the XTAL2 pin for no clock output as an indication that the device has entered the partial sleep mode. The UART portion in the L400 resumes normal operation or active mode by any of the following: ■ a receive data start bit transition on the RX inputs ■ a data byte is loaded to the transmitter, THR or FIFO ■ a change of logic state on any of the modem or general purpose serial inputs: i.e., any of the MSR bits 03 shows a ’1’ (in internal loopback mode) If the sleep mode is enabled and the L400 is awakened by one of the conditions described above, an interrupt is issued by the L400 to signal to the CPU that it is awake. The lower nibble of the interrupt source register (ISR) will read a value of 0x1 for this interrupt and reading the ISR clears this interrupt. Since the same value (0x1) is also used to indicate no pending interrupt, users should exercise caution while using the sleep mode. The UART portion in the L400 will return to the sleep mode automatically after all interrupting conditions have been serviced and cleared. If the UART portion of the L400 is awakened by the modem inputs, a read to the MSR is required to reset the modem inputs. In any case, the sleep mode will not be entered while an interrupt is pending. The UART portion of the L400 will stay in the sleep mode of operation until it is disabled by setting IER bit-4 to a logic 0. 2.12.1.1 Receiving data in UART sleep mode There is a start-up delay for the crystal oscillator after waking up from sleep mode, therefore the first few receive characters may be lost. The number of characters lost during the restart also depends on your operating data rate. More characters are lost when operating at higher data rate. If an external oscillator is used, any data received will be transferred to/from the UART without any issues. 2.12.2 UART active, Charge pump of RS-485 transceiver shut down (3.3V operation only) If the ACP pin is HIGH and the UART portion of the L400 is not in sleep mode, then the charge pump will automatically shut down to conserve power if the following conditions are true: ■ no activity on the TX output signals ■ modem inputs have been idle for approximately 30 seconds When these conditions are satisfied, the L400 shuts down the charge pump and tri-states the RS-485 drivers to conserve power. In this mode, the RS-485 receivers are fully active and the internal registers of the L400 can be accessed. The time for the charge pump to resume normal operation after exiting the sleep mode is typically 45s. It will wake up by any of the following: ■ a receive data start bit transition on the RX input (LOW to HIGH) ■ a data byte is loaded to the transmitter, THR or FIFO ■ a LOW to HIGH transition on any of the modem or general purpose serial inputs Because the receivers are fully active when the charge pump is turned off, any data received will be transferred to/from the UART without any issues. 2.12.2.1 Transmitting data in ACP Mode 16 XR19L400 REV. 1.0.4 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER Since it takes the charge pump typically 45s to resume normal operation after ACP mode has been disabled. It is recommended that data not be transmitted until after this time. 17 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER 2.12.3 REV. 1.0.4 UART sleep, Charge pump of RS-485 transceiver shut down (3.3V operation only) If the ACP pin is HIGH and the UART portion of the L400 is in sleep mode, then the charge pump will shut down immediately. In this mode, the L400 shuts down the charge pump and tri-states the RS-485 drivers to conserve power. In this mode, the RS-485 receivers are fully active and the internal registers of the L400 can be accessed. The time for the charge pump to resume normal operation after exiting the sleep mode is typically 45s. It will wake up by any of the following: ■ a receive data start bit transition on the RX input (LOW to HIGH) ■ a data byte is loaded to the transmitter, THR or FIFO ■ a LOW to HIGH transition on any of the modem or general purpose serial inputs 2.12.3.1 Receiving data in UART sleep mode There is a start-up delay for the crystal oscillator after waking up from sleep mode, therefore the first few receive characters may be lost. The number of characters lost during the restart also depends on your operating data rate. More characters are lost when operating at higher data rate. If an external oscillator is used, any data received will be transferred to/from the UART without any issues. 2.12.3.2 Transmitting data in ACP mode Since it takes the charge pump typically 45s to resume normal operation after ACP mode has been disabled. It is recommended that data not be transmitted until after this time. 2.12.4 Power-Save Feature This mode is in addition to the sleep mode and in this mode, the core logic of the L400 is isolated from the CPU interface. If the address lines, data bus lines, IOW#, IOR# and CS# remain steady when the L400 is in full sleep mode, the maximum current will be in the microamp range as specified in the DC Electrical Characteristics on page 37. However, if the input lines are floating or are toggling while the L400 is in sleep mode, the current can be up to 100 times more. If not using the Power-Save feature, an external buffer would be required to keep the address and data bus lines from toggling or floating to achieve the low current. But if the Power-Save feature is enabled (PwrSave pin connected to VCC), this will eliminate the need for an external buffer by internally isolating the address, data and control signals from other bus activities that could cause wasteful power drain (see Figure 1). The L400 enters Power-Save mode when this pin is connected to VCC, and the UART portion of the L400 is already in sleep mode. Since Power-Save mode isolates the address, data and control signals, the device will wake-up only by: ■ a receive data start bit transition, or ■ a change of logic state on any of the modem or general purpose serial inputs: i.e., any of the MSR bits 03 shows a ’1’ The L400 will return to the Power-Save mode automatically after a read to the MSR (to reset the modem inputs) and all interrupting conditions have been serviced and cleared. The L400 will stay in the Power-Save mode of operation until it is disabled by setting IER bit-4 to a logic 0 and/or the Power-Save pin is connected to GND. If the L400 is awakened by any one of the above conditions, it issues an interrupt as soon as the oscillator circuit is up and running and the device is ready to transmit/receive. This interrupt has the same encoding (bit0 of ISR register = 1) as "no interrupt pending" and will clear when the ISR register is read. This will show up in the ISR register only if no other interrupts are enabled. 18 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 2.13 Internal Loopback The L400 UART provides an internal loopback capability for system diagnostic purposes. The internal loopback mode is enabled by setting MCR register bit-4 to logic 1. All regular UART functions operate normally. Figure 11 shows how the modem port signals are re-configured. Transmit data from the transmit shift register output is internally routed to the receive shift register input allowing the system to receive the same data that it was sending. FIGURE 11. INTERNAL LOOP BACK VCC TX Transmit Shift Register (THR/FIFO) Receive Shift Register (RHR/FIFO) RX VCC RTS# RTS Modem / General Purpose Control Logic Internal Data Bus Lines and Control Signals MCR bit-4=1 CTS CTS# VCC DTR# DTR DSR DSR# OP1# RI RI# OP2# CD 19 CD# XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 3.0 UART INTERNAL REGISTERS The L400 has a set of configuration registers selected by address lines A0, A1 and A2 with CS# asserted. The complete register set is shown on Table 5 and Table 6. TABLE 5: UART INTERNAL REGISTERS ADDRESSES A2 A1 A0 REGISTER READ/WRITE COMMENTS LCR[7] = 0 16C550 COMPATIBLE REGISTERS 0 0 0 RHR - Receive Holding Register THR - Transmit Holding Register Read-only Write-only 0 0 0 DLL - Divisor LSB Read/Write 0 0 1 DLM - Divisor MSB Read/Write 0 1 0 DLD - Divisor Fractional Read/Write LCR[7] = 1, LCR  0xBF, EFR[4] = 1 0 0 0 DREV - Device Revision Code Read-only 0 0 1 DVID - Device Identification Code Read-only DLL, DLM 0x00, LCR[7] = 1, LCR  0xBF 0 0 1 IER - Interrupt Enable Register Read/Write LCR[7] = 0 0 1 0 ISR - Interrupt Status Register FCR - FIFO Control Register Read-only Write-only LCR  0xBF 0 1 1 LCR - Line Control Register Read/Write 1 0 0 MCR - Modem Control Register Read/Write 1 0 1 LSR - Line Status Register Read-only 1 1 0 MSR - Modem Status Register Read-only 1 1 1 SPR - Scratch Pad Register Read/Write 1 1 1 FLVL - RX/TX FIFO Level Counter Register Read-only 1 1 1 EMSR - Enhanced Mode Select Register Write-only LCR[7] = 1, LCR  0xBF LCR  0xBF LCR  0xBF, FCTR[6] = 0 LCR  0xBF, FCTR[6] = 1 ENHANCED REGISTERS 0 0 0 TRG - RX/TX FIFO Trigger Level Register FC - RX/TX FIFO Level Counter Register Write-only Read-only 0 0 1 FCTR - Feature Control Register Read/Write 0 1 0 EFR - Enhanced Function Register Read/Write 1 0 0 Xon-1 - Xon Character 1 Read/Write 1 0 1 Xon-2 - Xon Character 2 Read/Write 1 1 0 Xoff-1 - Xoff Character 1 Read/Write 1 1 1 Xoff-2 - Xoff Character 2 Read/Write 20 LCR = 0xBF XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 . TABLE 6: INTERNAL REGISTERS DESCRIPTIONS. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1 ADDRESS A2-A0 REG NAME READ/ WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT 16C550 Compatible Registers 000 RHR RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 000 THR WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 001 IER RD/WR 0/ 0/ 0/ 0/ Rsrvd Rsrvd Xoff Int. Enable Sleep Mode Enable 0/ 0/ INT Source Bit-5 INT Source Bit-4 0/ 0/ 010 010 ISR FCR RD WR FIFOs FIFOs Enabled Enabled RX FIFO RX FIFO Trigger Trigger Modem RX Line TX RX Stat. Int. Stat. Empty Data Enable Int. Int Int. Enable Enable Enable INT Source Bit-3 INT INT INT Source Source Source Bit-2 Bit-1 Bit-0 Rsrvd TX FIFO Reset Parity Enable Stop Bits TX FIFO TX FIFO Trigger Trigger 011 LCR RD/WR Divisor Enable Set TX Break Set Parity 100 MCR RD/WR 0/ 0/ 0/ BRG Prescaler Rsrvd Even Parity RX FIFO Reset FIFOs Enable Internal OP2#/INT Rsrvd RTS# DTR# Lopback Output (OP1#) Output Output XonAny Enable Enable Control Control LSR RD RX FIFO Global Error THR & TSR Empty THR Empty RX Break RX Framing Error RX Parity Error RX Overrun Error RX Data Ready 110 MSR RD CD# Input RI# Input DSR# Input CTS# Input Delta CD# Delta RI# Delta DSR# Delta CTS# 111 SPR RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 111 EMSR WR 16X Sampling Rate Mode LSR Error Interrupt. Imd/Dly# Auto RTS Hyst. bit-3 Auto RTS Hyst. bit-2 Rsrvd Rsrvd Rx/Tx FIFO Count Rx/Tx FIFO Count Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 FLVL RD LCR  0xBF Word Word Length Length Bit-1 Bit-0 101 111 LCR[7]=0 21 LCR  0xBF LCR  0xBF FCTR[6]=0 LCR  0xBF FCTR[6]=1 Bit-2 Bit-1 Bit-0 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 TABLE 6: INTERNAL REGISTERS DESCRIPTIONS. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1 ADDRESS A2-A0 REG NAME READ/ WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT LCR[7]=1 LCR  0xBF Baud Rate Generator Divisor 000 DLL RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 001 DLM RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 010 DLD RD/WR 0 0 0 0 Bit-3 Bit-2 Bit-1 Bit-0 LCR[7]=1 LCR  0xBF EFR[4] = 1 000 DREV RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 001 DVID RD 0 0 0 0 1 0 1 0 LCR[7]=1 LCR  0xBF DLL=0x00 DLM=0x00 Enhanced Registers 000 TRG WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 000 FC RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 RX/TX Mode SCPAD Swap Trig Table Bit-1 Trig Table Bit-0 Auto Half- Rsrvd Duplex Direction Control Auto RTS Hyst Bit-1 Auto RTS Hyst Bit-0 Rsrvd Rsrvd Rsrvd 001 010 FCTR RD/WR EFR RD/WR Software Flow Cntl Bit-2 Software Flow Cntl Bit-1 Software Flow Cntl Bit-0 DLD Software Flow Cntl Bit-3 Enable IER [7:4], ISR [5:4], FCR[5:4], MCR[7:5], 100 XON1 RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 101 XON2 RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 110 XOFF1 RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 111 XOFF2 RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 LCR=0XBF 4.0 INTERNAL REGISTER DESCRIPTIONS 4.1 Receive Holding Register (RHR) - Read- Only SEE”RECEIVER” ON PAGE 13. 4.2 Transmit Holding Register (THR) - Write-Only SEE”TRANSMITTER” ON PAGE 12. 4.3 Interrupt Enable Register (IER) - Read/Write The Interrupt Enable Register (IER) masks the interrupts from receive data ready, transmit empty, line status and modem status registers. These interrupts are reported in the Interrupt Status Register (ISR). 22 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 4.3.1 IER versus Receive FIFO Interrupt Mode Operation When the receive FIFO (FCR BIT-0 = 1) and receive interrupts (IER BIT-0 = 1) are enabled, the RHR interrupts (see ISR bits 2 and 3) status will reflect the following: A. The receive data available interrupts are issued to the host when the FIFO has reached the programmed trigger level. It will be cleared when the FIFO drops below the programmed trigger level. B. FIFO level will be reflected in the ISR register when the FIFO trigger level is reached. Both the ISR register status bit and the interrupt will be cleared when the FIFO drops below the trigger level. C. The receive data ready bit (LSR BIT-0) is set as soon as a character is transferred from the shift register to the receive FIFO. It is reset when the FIFO is empty. 4.3.2 IER versus Receive/Transmit FIFO Polled Mode Operation When FCR BIT-0 equals a logic 1 for FIFO enable; resetting IER bits 0-3 enables the XR19L400 in the FIFO polled mode of operation. Since the receiver and transmitter have separate bits in the LSR either or both can be used in the polled mode by selecting respective transmit or receive control bit(s). A. LSR BIT-0 indicates there is data in RHR or RX FIFO. B. LSR BIT-1 indicates an overrun error has occurred and that data in the FIFO may not be valid. C. LSR BIT 2-4 provides the type of receive data errors encountered for the data byte in RHR, if any. D. LSR BIT-5 indicates THR is empty. E. LSR BIT-6 indicates when both the transmit FIFO and TSR are empty. F. LSR BIT-7 indicates a data error in at least one character in the RX FIFO. IER[0]: RHR Interrupt Enable The receive data ready interrupt will be issued when RHR has a data character in the non-FIFO mode or when the receive FIFO has reached the programmed trigger level in the FIFO mode.  Logic 0 = Disable the receive data ready interrupt (default).  Logic 1 = Enable the receiver data ready interrupt. IER[1]: THR Interrupt Enable This bit enables the Transmit Ready interrupt which is issued whenever the THR becomes empty in the nonFIFO mode or when data in the FIFO falls below the programmed trigger level in the FIFO mode. If the THR is empty when this bit is enabled, an interrupt will be generated.  Logic 0 = Disable Transmit Ready interrupt (default).  Logic 1 = Enable Transmit Ready interrupt. IER[2]: Receive Line Status Interrupt Enable If any of the LSR register bits 1, 2, 3 or 4 is a logic 1, it will generate an interrupt to inform the host controller about the error status of the current data byte in FIFO. LSR bit-1 generates an interrupt immediately when the character has been received. LSR bits 2-4 generate an interrupt when the character with errors is read out of the FIFO (default). Instead, LSR bits 2-4 can be programmed to generate an interrupt immediately, by setting EMSR bit-6 to a logic 1.  Logic 0 = Disable the receiver line status interrupt (default).  Logic 1 = Enable the receiver line status interrupt. IER[3]: Modem Status Interrupt Enable  Logic 0 = Disable the modem status register interrupt (default).  Logic 1 = Enable the modem status register interrupt. 23 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 IER[4]: Sleep Mode Enable (requires EFR bit-4 = 1)  Logic 0 = Disable Sleep Mode (default).  Logic 1 = Enable Sleep Mode. See Sleep Mode section for further details. IER[5]: Xoff Interrupt Enable (requires EFR bit-4=1)  Logic 0 = Disable the software flow control, receive Xoff interrupt (default).  Logic 1 = Enable the software flow control, receive Xoff interrupt. See Software Flow Control section for details. IER[7:6]: Reserved For normal operation, these bits should remain at logic 0. 4.4 Interrupt Status Register (ISR) - Read-Only The UART provides multiple levels of prioritized interrupts to minimize external software interaction. The Interrupt Status Register (ISR) provides the user with six interrupt status bits. Performing a read cycle on the ISR will give the user the current highest pending interrupt level to be serviced, others are queued up to be serviced next. No other interrupts are acknowledged until the pending interrupt is serviced. The Interrupt Source Table, Table 7, shows the data values (bit 0-5) for the interrupt priority levels and the interrupt sources associated with each of these interrupt levels. 4.4.1 Interrupt Generation:  LSR is by any of the LSR bits 1, 2, 3 and 4.  RXRDY is by RX trigger level.  RXRDY Time-out is by a 4-char plus 12 bits delay timer.  TXRDY is by TX trigger level or TX FIFO empty (or transmitter empty in auto half-duplex control).  MSR is by any of the MSR bits 0, 1, 2 and 3.  Receive Xoff is by detection of a Xoff character.  Wake-up Indicator is when the UART comes out of sleep mode. 4.4.2 Interrupt Clearing:  LSR interrupt is cleared by a read to the LSR register.  RXRDY interrupt is cleared by reading data until FIFO falls below the trigger level.  RXRDY Time-out interrupt is cleared by reading RHR.  TXRDY interrupt is cleared by a read to the ISR register or writing to THR.  MSR interrupt is cleared by a read to the MSR register.  Xoff interrupt is cleared by a read to ISR or when Xon character(s) is received.  Wake-up Indicator is cleared by a read to the ISR register. 24 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 ] TABLE 7: INTERRUPT SOURCE AND PRIORITY LEVEL PRIORITY ISR REGISTER STATUS BITS SOURCE OF INTERRUPT LEVEL BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 1 0 0 0 1 1 0 LSR (Receiver Line Status Register) 2 0 0 1 1 0 0 RXRDY (Receive Data Time-out) 3 0 0 0 1 0 0 RXRDY (Received Data Ready) 4 0 0 0 0 1 0 TXRDY (Transmit Ready) 5 0 0 0 0 0 0 MSR (Modem Status Register) 6 0 1 0 0 0 0 RXRDY (Received Xoff character) - 0 0 0 0 0 1 None (default) or Wake-up Indicator ISR[0]: Interrupt Status  Logic 0 = An interrupt is pending and the ISR contents may be used as a pointer to the appropriate interrupt service routine.  Logic 1 = No interrupt pending (default condition) or the device has come out of sleep mode. ISR[3:1]: Interrupt Status These bits indicate the source for a pending interrupt at interrupt priority levels (See Interrupt Source Table 7). ISR[4]: Xoff Character Interrupt Status (requires EFR bit-4=1) This bit is enabled when IER[5] = 1. ISR bit-4 indicates that the receiver detected a data match of the Xoff character(s). ISR[5]: Reserved For normal operation, this bit should remain a logic 0. ISR[7:6]: FIFO Enable Status These bits are set to a logic 0 when the FIFOs are disabled. They are set to a logic 1 when the FIFOs are enabled. 4.5 FIFO Control Register (FCR) - Write-Only This register is used to enable the FIFOs, clear the FIFOs, and set the transmit/receive FIFO trigger levels. FCR[0]: TX and RX FIFO Enable  Logic 0 = Disable the transmit and receive FIFO (default).  Logic 1 = Enable the transmit and receive FIFOs. This bit must be set to logic 1 when other FCR bits are written or they will not be programmed. FCR[1]: RX FIFO Reset This bit is only active when FCR bit-0 is a ‘1’.  Logic 0 = No receive FIFO reset (default)  Logic 1 = Reset the receive FIFO pointers and FIFO level counter logic (the receive shift register is not cleared or altered). This bit will return to a logic 0 after resetting the FIFO. 25 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FCR[2]: TX FIFO Reset This bit is only active when FCR bit-0 is a ‘1’.  Logic 0 = No transmit FIFO reset (default).  Logic 1 = Reset the transmit FIFO pointers and FIFO level counter logic (the transmit shift register is not cleared or altered). This bit will return to a logic 0 after resetting the FIFO. FCR[3]: Reserved For normal operation, this bit should remain a logic 0. FCR[5:4]: Transmit FIFO Trigger Select (requires EFR bit-4=1) (logic 0 = default, TX trigger level = 1) These 2 bits set the trigger level for the transmit FIFO. The UART will issue a transmit interrupt when the number of characters in the FIFO falls below the selected trigger level, or when it gets empty in case that the FIFO did not get filled over the trigger level on last re-load. Table 8 below shows the selections. EFR bit-4 must be set to ‘1’ before these bits can be accessed. Note that the receiver and the transmitter cannot use different trigger tables. Whichever selection is made last applies to both the RX and TX side. FCR[7:6]: Receive FIFO Trigger Select (logic 0 = default, RX trigger level =1) The FCTR Bits 5-4 are associated with these 2 bits. These 2 bits are used to set the trigger level for the receive FIFO. The UART will issue a receive interrupt when the number of the characters in the FIFO crosses the trigger level. Table 8 shows the complete selections. Note that the receiver and the transmitter cannot use different trigger tables. Whichever selection is made last applies to both the RX and TX side. TABLE 8: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION TRIGGER TABLE FCTR BIT-5 FCTR BIT-4 Table-A 0 0 Table-B 0 FCR BIT-7 FCR BIT-6 0 0 1 1 0 1 0 1 1 FCR BIT-5 FCR BIT-4 0 0 TRANSMIT TRIGGER LEVEL 1 (default) 1 (default) 4 8 14 0 0 1 1 0 0 1 1 RECEIVE TRIGGER LEVEL 0 1 0 1 0 1 0 1 16 8 24 30 8 16 24 28 26 COMPATIBILITY 16C550, 16C2550, 16C2552, 16C554, 16C580 16C650A XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 TABLE 8: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION TRIGGER TABLE FCTR BIT-5 FCTR BIT-4 Table-C 1 0 Table-D 4.6 1 1 FCR BIT-7 FCR BIT-6 0 0 1 1 0 1 0 1 X X FCR BIT-5 FCR BIT-4 0 0 1 1 0 1 0 1 RECEIVE TRIGGER LEVEL TRANSMIT TRIGGER LEVEL 8 16 32 56 COMPATIBILITY 16C654 8 16 56 60 X X Programmable Programmable 16L2752, 16C2850, 16C2852, 16C850, via TRG via TRG 16C854, 16C864 register. register. FCTR[7] = 1. FCTR[7] = 0. Line Control Register (LCR) - Read/Write The Line Control Register is used to specify the asynchronous data communication format. The word or character length, the number of stop bits, and the parity are selected by writing the appropriate bits in this register. LCR[1:0]: TX and RX Word Length Select These two bits specify the word length to be transmitted or received. BIT-1 BIT-0 WORD LENGTH 0 0 5 (default) 0 1 6 1 0 7 1 1 8 LCR[2]: TX and RX Stop-bit Length Select The length of stop bit is specified by this bit in conjunction with the programmed word length. LENGTH STOP BIT LENGTH (BIT TIME(S)) 0 5,6,7,8 1 (default) 1 5 1-1/2 1 6,7,8 2 BIT-2 WORD 27 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 LCR[3]: TX and RX Parity Select Parity or no parity can be selected via this bit. The parity bit is a simple way used in communications for data integrity check. See Table 9 for parity selection summary below.  Logic 0 = No parity.  Logic 1 = A parity bit is generated during the transmission while the receiver checks for parity error of the data character received. LCR[4]: TX and RX Parity Select If the parity bit is enabled with LCR bit-3 set to a logic 1, LCR bit-4 selects the even or odd parity format.  Logic 0 = ODD Parity is generated by forcing an odd number of logic 1’s in the transmitted character. The receiver must be programmed to check the same format (default).  Logic 1 = EVEN Parity is generated by forcing an even number of logic 1’s in the transmitted character. The receiver must be programmed to check the same format. LCR[5]: TX and RX Parity Select If the parity bit is enabled, LCR BIT-5 selects the forced parity format.  LCR BIT-5 = logic 0, parity is not forced (default).  LCR BIT-5 = logic 1 and LCR BIT-4 = logic 0, parity bit is forced to a logical 1 for the transmit and receive data.  LCR BIT-5 = logic 1 and LCR BIT-4 = logic 1, parity bit is forced to a logical 0 for the transmit and receive data. TABLE 9: PARITY SELECTION LCR BIT-5 LCR BIT-4 LCR BIT-3 PARITY SELECTION X X 0 No parity 0 0 1 Odd parity 0 1 1 Even parity 1 0 1 Force parity to mark, “1” 1 1 1 Forced parity to space, “0” LCR[6]: Transmit Break Enable When enabled, the Break control bit causes a break condition to be transmitted (the TX output is forced to a “space", LOW state). This condition remains, until disabled by setting LCR bit-6 to a logic 0.  Logic 0 = No TX break condition (default).  Logic 1 = Forces the transmitter output (TX) to a “space”, LOW, for alerting the remote receiver of a line break condition. LCR[7]: Baud Rate Divisors Enable Baud rate generator divisor (DLL, DLM and DLD) enable.  Logic 0 = Data registers are selected (default).  Logic 1 = Divisor latch registers are selected. 28 XR19L400 REV. 1.0.4 4.7 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER Modem Control Register (MCR) or General Purpose Outputs Control - Read/Write The MCR register is used for controlling the serial/modem interface signals or general purpose inputs/outputs. MCR[0]: DTR# Output DTR# is not available as an output pin on the L400, but it is available for use during internal loopback mode. In internal loopback mode, this bit is used to write the state of the DSR# interface signal.  Logic 0 = Force DTR# output HIGH (default).  Logic 1 = Force DTR# output LOW. MCR[1]: RTS# Output RTS# is not available as an output pin on the L400, but it is available for use during internal loopback mode. In internal loopback mode, this bit is used to write the state of the CTS# interface signal. If half-duplex mode is enabled via the Half/Full# pin or in is a modem control output and may be used for automatic hardware flow control by enabled by EFR bit-6. The RTS# pin can also be used for Auto RS485 Half-Duplex direction control enabled by FCTR bit-3. If the modem interface is not used, this output may be used as a general purpose output.  Logic 0 = Force RTS# HIGH (default).  Logic 1 = Force RTS# LOW. MCR[2]: Reserved OP1# is not available as an output pin on the L400. But it is available for use during Internal Loopback Mode. In the Loopback Mode, this bit is used to write the state of the modem RI# interface signal. MCR[3]: OP2# Output / INT Output Enable This bit enables or disables the operation of INT, interrupt output. If INT output is not used, OP2# can be used as a general purpose output. Also, if 16/68# pin selects Motorola bus interface mode, this bit must be set to logic 0.  Logic 0 = INT (A-B) outputs disabled (three state mode) and OP2# output set HIGH(default).  Logic 1 = INT (A-B) outputs enabled (active mode) and OP2# output set LOW. MCR[4]: Internal Loopback Enable  Logic 0 = Disable loopback mode (default).  Logic 1 = Enable local loopback mode, see loopback section and Figure 11. MCR[5]: Xon-Any Enable (requires EFR bit-4=1)  Logic 0 = Disable Xon-Any function (default).  Logic 1 = Enable Xon-Any function. In this mode, any RX character received will resume transmit operation. The RX character will be loaded into the RX FIFO, unless the RX character is an Xon or Xoff character and the L400 is programmed to use the Xon/Xoff flow control. MCR[6]: Reserved For normal operation, this bit should remain a logic 0. MCR[7]: Clock Prescaler Select (requires EFR bit-4=1)  Logic 0 = Divide by one. The input clock from the crystal or external clock is fed directly to the Programmable Baud Rate Generator without further modification, i.e., divide by one (default).  Logic 1 = Divide by four. The prescaler divides the input clock from the crystal or external clock by four and feeds it to the Programmable Baud Rate Generator, hence, data rates become one forth. 29 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER 4.8 REV. 1.0.4 Line Status Register (LSR) - Read Only This register provides the status of data transfers between the UART and the host. LSR[0]: Receive Data Ready Indicator  Logic 0 = No data in receive holding register or FIFO (default).  Logic 1 = Data has been received and is saved in the receive holding register or FIFO. LSR[1]: Receiver Overrun Error Flag  Logic 0 = No overrun error (default).  Logic 1 = Overrun error. A data overrun error condition occurred in the receive shift register. This happens when additional data arrives while the FIFO is full. In this case the previous data in the receive shift register is overwritten. Note that under this condition the data byte in the receive shift register is not transferred into the FIFO, therefore the data in the FIFO is not corrupted by the error. LSR[2]: Receive Data Parity Error Tag  Logic 0 = No parity error (default).  Logic 1 = Parity error. The receive character in RHR does not have correct parity information and is suspect. This error is associated with the character available for reading in RHR. LSR[3]: Receive Data Framing Error Tag  Logic 0 = No framing error (default).  Logic 1 = Framing error. The receive character did not have a valid stop bit(s). This error is associated with the character available for reading in RHR. LSR[4]: Receive Break Error Tag  Logic 0 = No break condition (default).  Logic 1 = The receiver received a break signal (RX was LOW for at least one character frame time). In the FIFO mode, only one break character is loaded into the FIFO. LSR[5]: Transmit Holding Register Empty Flag This bit is the Transmit Holding Register Empty indicator. The THR bit is set to a logic 1 when the last data byte is transferred from the transmit holding register to the transmit shift register. The bit is reset to logic 0 concurrently with the data loading to the transmit holding register by the host. In the FIFO mode this bit is set when the transmit FIFO is empty, it is cleared when the transmit FIFO contains at least 1 byte. LSR[6]: THR and TSR Empty Flag This bit is set to a logic 1 whenever the transmitter goes idle. It is set to logic 0 whenever either the THR or TSR contains a data character. In the FIFO mode this bit is set to a logic 1 whenever the transmit FIFO and transmit shift register are both empty. LSR[7]: Receive FIFO Data Error Flag  Logic 0 = No FIFO error (default).  Logic 1 = A global indicator for the sum of all error bits in the RX FIFO. At least one parity error, framing error or break indication is in the FIFO data. This bit clears when there is no more error(s) in any of the bytes in the RX FIFO. 4.9 Modem Status Register (MSR) - Read Only This register provides the current state of the modem interface input signals. Lower four bits of this register are used to indicate the changed information. These bits are set to a logic 1 whenever a signal from the modem changes state. These bits may be used for general purpose inputs when they are not used with modem signals. 30 XR19L400 REV. 1.0.4 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER MSR[0]: Delta CTS# Input Flag (Internal Loopback Mode Only)  Logic 0 = No change on CTS# input (default).  Logic 1 = The CTS# input has changed state since the last time it was monitored. A modem status interrupt will be generated if MSR interrupt is enabled (IER bit-3). MSR[1]: Delta DSR# Input Flag (Internal Loopback Mode Only)  Logic 0 = No change on DSR# input (default).  Logic 1 = The DSR# input has changed state since the last time it was monitored. A modem status interrupt will be generated if MSR interrupt is enabled (IER bit-3). MSR[2]: Delta RI# Input Flag (Internal Loopback Mode Only)  Logic 0 = No change on RI# input (default).  Logic 1 = The RI# input has changed from a LOW to HIGH, ending of the ringing signal. A modem status interrupt will be generated if MSR interrupt is enabled (IER bit-3). MSR[3]: Delta CD# Input Flag (Internal Loopback Mode Only)  Logic 0 = No change on CD# input (default).  Logic 1 = Indicates that the CD# input has changed state since the last time it was monitored. A modem status interrupt will be generated if MSR interrupt is enabled (IER bit-3). MSR[4]: CTS Input Status CTS# is not available as an input pin on the L400, but it is available for use during internal loopback mode. This bit is equivalent to the RTS# bit in the MCR register. MSR[5]: DSR Input Status CTS# is not available as an input pin on the L400, but it is available for use during internal loopback mode. This bit is equivalent to the DTR# bit in the MCR register. MSR[6]: RI Input Status RI# is not available as an input pin on the L400, but it is available for use during internal loopback mode. This bit is equivalent to bit-2 in the MCR register. MSR[7]: CD Input Status CD# is not available as an input pin on the L400, but it is available for use during internal loopback mode. This bit is equivalent to bit-3 in the MCR register. 4.10 Scratch Pad Register (SPR) - Read/Write This is a 8-bit general purpose register for the user to store temporary data. The content of this register is preserved during sleep mode but becomes 0xFF (default) after a reset or a power off-on cycle. 4.11 Enhanced Mode Select Register (EMSR) This register replaces SPR (during a Write) and is accessible only when FCTR[6] = 1. 31 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 EMSR[1:0]: Receive/Transmit FIFO Level Count (Write-Only) When Scratchpad Swap (FCTR[6]) is asserted, EMSR bits 1-0 controls what mode the FIFO Level Counter is operating in. TABLE 10: SCRATCHPAD SWAP SELECTION FCTR[6] EMSR[1] EMSR[0] Scratchpad is 0 X X Scratchpad 1 X 0 RX FIFO Level Counter Mode 1 0 1 TX FIFO Level Counter Mode 1 1 1 Alternate RX/TX FIFO Counter Mode During Alternate RX/TX FIFO Level Counter Mode, the first value read after EMSR bits 1-0 have been asserted will always be the RX FIFO Level Counter. The second value read will correspond with the TX FIFO Level Counter. The next value will be the RX FIFO Level Counter again, then the TX FIFO Level Counter and so on and so forth. EMSR[3:2]: Reserved For normal operation, these bits should remain a logic 0. EMSR[5:4]: Extended RTS Hysteresis TABLE 11: XON/XOFF HYSTERESIS EMSR BIT-5 EMSR BIT-4 FCTR BIT-1 FCTR BIT-0 XON/XOFF HYSTERESIS (CHARACTERS) 0 0 0 0 0 0 0 0 0 0 1 1 0 1 0 1 0 ±4 ±6 ±8 0 0 0 0 1 1 1 1 0 0 1 1 0 1 0 1 ±8 ±16 ±24 ±32 1 1 1 1 0 0 0 0 0 0 1 1 0 1 0 1 ±40 ±44 ±48 ±52 1 1 1 1 1 1 1 1 0 0 1 1 0 1 0 1 ±12 ±20 ±28 ±36 EMSR[6]: LSR Interrupt Mode  Logic 0 = LSR Interrupt Delayed (for 16C2550 compatibility, default). LSR bits 2, 3, and 4 will generate an interrupt when the character with the error is in the RHR.  Logic 1 = LSR Interrupt Immediate. LSR bits 2, 3, and 4 will generate an interrupt as soon as the character is received into the FIFO. 32 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 EMSR[7]: 16X Sampling Rate Mode Logic 0 = 8X Sampling Rate. Logic 1 = 16X Sampling Rate (default). 4.12 FIFO Level Register (FLVL) - Read-Only The FIFO Level Register replaces the Scratchpad Register (during a Read) when FCTR[6] = 1. Note that this is not identical to the FIFO Data Count Register which can be accessed when LCR = 0xBF. FLVL[7:0]: FIFO Level Register This register provides the FIFO counter level for the RX FIFO or the TX FIFO or both depending on EMSR[1:0]. See Table 10 for details. 4.13 Baud Rate Generator Registers (DLL, DLM and DLD) - Read/Write These registers make-up the value of the baud rate divisor. The concatenation of the contents of DLM and DLL is a 16-bit value is then added to DLD/16 to achieve the fractional baud rate divisor. DLD must be enabled via EFR bit-4 before it can be accessed. SEE”PROGRAMMABLE BAUD RATE GENERATOR WITH FRACTIONAL DIVISOR” ON PAGE 9. 4.14 Device Identification Register (DVID) - Read Only This register contains the device ID (0x0A). Prior to reading this register, DLL and DLM should be set to 0x00 (DLD = 0xXX). 4.15 Device Revision Register (DREV) - Read Only This register contains the device revision information. For example, 0x01 means revision A. Prior to reading this register, DLL and DLM should be set to 0x00 (DLD = 0xXX). 4.16 Trigger Level Register (TRG) - Write-Only User Programmable Transmit/Receive Trigger Level Register. If both the TX and RX trigger levels are used, the TX trigger levels must be set before the RX trigger levels. TRG[7:0]: Trigger Level Register These bits are used to program desired trigger levels when trigger Table-D is selected. FCTR bit-7 selects between programming the RX Trigger Level (a logic 0) and the TX Trigger Level (a logic 1). 4.17 RX/TX FIFO Level Count Register (FC) - Read-Only This register is accessible when LCR = 0xBF. Note that this register is not identical to the FIFO Level Count Register which is located in the general register set when FCTR bit-6 = 1 (Scratchpad Register Swap). It is suggested to read the FIFO Level Count Register at the Scratchpad Register location when FCTR bit-6 = 1. See Table 10. FC[7:0]: RX/TX FIFO Level Count Receive/Transmit FIFO Level Count. Number of characters in Receiver FIFO (FCTR[7] = 0) or Transmitter FIFO (FCTR[7] = 1) can be read via this register. Reading this register is not recommended when transmitting or receiving data. 4.18 Feature Control Register (FCTR) - Read/Write FCTR[2:0]: Reserved For normal operation, these bits should remain a logic 0. 33 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FCTR[3]: Auto Half-Duplex Direction Control This bit overrides the HALF/FULL# pin to enable half-duplex mode or full-duplex mode.  Logic 0 = Full-duplex mode. In this mode, the transmit interrupt is generated when the transmit holding register becomes empty and the transmit shift register is shifting data out.  Logic 1 = Auto half-duplex mode. In this mode, the direction of the RS-485 transceiver is internally controlled by the RTS# signal. Also, the transmit interrupt generation is delayed until the transmitter shift register becomes empty. FCTR[5:4]: Transmit/Receive Trigger Table Select See Table 8 for more details. TABLE 12: TRIGGER TABLE SELECT FCTR BIT-5 FCTR BIT-4 0 0 Table-A (TX/RX) 0 1 Table-B (TX/RX) 1 0 Table-C (TX/RX) 1 1 Table-D (TX/RX) TABLE FCTR[6]: Scratchpad Swap  Logic 0 = Scratch Pad register is selected as general read and write register. ST16C550 compatible mode.  Logic 1 = FIFO Level Count register (Read-Only), Enhanced Mode Select Register (Write-Only). Number of characters in transmit or receive FIFO can be read via scratch pad register when this bit is set. Enhanced Mode Select Register is selected when it is written into. FCTR[7]: Programmable Trigger Register Select If using both programmable TX and RX trigger levels, TX trigger levels must be set before RX trigger levels.  Logic 0 = Registers TRG and FC selected for RX.  Logic 1 = Registers TRG and FC selected for TX. 4.19 Enhanced Feature Register (EFR) Enhanced features are enabled or disabled using this register. Bit 0-3 provide single or dual consecutive character software flow control selection (see Table 13). When the Xon1 and Xon2 and Xoff1 and Xoff2 modes are selected, the double 8-bit words are concatenated into two sequential characters. Caution: note that whenever changing the TX or RX flow control bits, always reset all bits back to logic 0 (disable) before programming a new setting. 34 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 EFR[3:0]: Software Flow Control Select Single character and dual sequential characters software flow control is supported. Combinations of software flow control can be selected by programming these bits. TABLE 13: SOFTWARE FLOW CONTROL FUNCTIONS EFR BIT-3 CONT-3 EFR BIT-2 CONT-2 EFR BIT-1 CONT-1 EFR BIT-0 CONT-0 0 0 0 0 No TX and RX flow control (default and reset) 0 0 X X No transmit flow control 1 0 X X Transmit Xon1, Xoff1 0 1 X X Transmit Xon2, Xoff2 1 1 X X Transmit Xon1 and Xon2, Xoff1 and Xoff2 X X 0 0 No receive flow control X X 1 0 Receiver compares Xon1, Xoff1 X X 0 1 Receiver compares Xon2, Xoff2 1 0 1 1 Transmit Xon1, Xoff1 Receiver compares Xon1 or Xon2, Xoff1 or Xoff2 0 1 1 1 Transmit Xon2, Xoff2 Receiver compares Xon1 or Xon2, Xoff1 or Xoff2 1 1 1 1 Transmit Xon1 and Xon2, Xoff1 and Xoff2, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 0 0 1 1 No transmit flow control, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL EFR[4]: Enhanced Function Bits Enable Enhanced function control bit. This bit enables IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 5-7, and DLD to be modified. After modifying any enhanced bits, EFR bit-4 can be set to a logic 0 to latch the new values. This feature prevents legacy software from altering or overwriting the enhanced functions once set. Normally, it is recommended to leave it enabled, logic 1.  Logic 0 = modification disable/latch enhanced features. IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 57, and DLD are saved to retain the user settings. After a reset, the IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 5-7, and DLD are set to a logic 0 to be compatible with ST16C550 mode (default).  Logic 1 = Enables the above-mentioned register bits to be modified by the user. EFR[7:5]: Reserved For normal operation, these bits should be at logic 0. 4.20 Software Flow Control Registers (XOFF1, XOFF2, XON1, XON2) - Read/Write These registers are used as the programmable software flow control characters xoff1, xoff2, xon1, and xon2. For more details, see Table 5. 35 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER TABLE 14: UART RESET CONDITIONS FOR CHANNEL A AND B REGISTERS RESET STATE DLM, DLL DLM = 0x00 and DLL = 0x01. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. DLD Bits 7-0 = 0x00 RHR Bits 7-0 = 0xXX THR Bits 7-0 = 0xXX IER Bits 7-0 = 0x00 FCR Bits 7-0 = 0x00 ISR Bits 7-0 = 0x01 LCR Bits 7-0 = 0x00 MCR Bits 7-0 = 0x00 LSR Bits 7-0 = 0x60 MSR Bits 3-0 = Logic 0 Bits 7-4 = Logic levels of the inputs inverted SPR Bits 7-0 = 0xFF EMSR Bits 7-0 = 0x80 FLVL Bits 7-0 = 0x00 TRG Bits 7-0 = 0x00 FC Bits 7-0 = 0x00 FCTR Bits 7-0 = 0x00 EFR Bits 7-0 = 0x00 XON1 Bits 7-0 = 0x00 XON2 Bits 7-0 = 0x00 XOFF1 Bits 7-0 = 0x00 XOFF2 Bits 7-0 = 0x00 I/O SIGNALS RESET STATE TX+/TX- RS-485 HIGH (Full-duplex mode) INT (IRQ#) Three-State Condition (16 mode) CMOS/TTL HIGH (68 mode) 36 REV. 1.0.4 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 ABSOLUTE MAXIMUM RATINGS Power Supply Range 5.5 Volts Voltage at Any Pin GND-0.3 V to 5.5 V Operating Temperature -40o to +85oC Storage Temperature -65o to +150oC TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: ± 15%) Thermal Resistance (40-QFN) theta-ja = 40oC/W, theta-jc = 13oC/W ELECTRICAL CHARACTERISTICS UNLESS OTHERWISE NOTED: TA= -40O TO +85OC (INDUSTRIAL GRADE), VCC= 3.3 or 5V ± 10% PARAMETER SYMBOL CONDITIONS 3.3V LIMITS MIN MAX 5.0V LIMITS MIN MAX UNITS DC CHARACTERISTICS ICC Supply Current, Normal Mode 60 ohm load 40 20 mA ISLP/IPWS Supply Current, Sleep Mode/PowerSave Mode 60 ohm load, ACP mode disabled (ACP mode applies to 3.3V only) 10 15 mA ISLP/IPWS Supply Current, Sleep Mode/PowerSave Mode 60 ohm load, ACP mode enabled (ACP mode applies to 3.3V only) 5 - mA OSCILLATOR INPUT (X1) VILCK Clock Input Low Level -0.3 0.6 -0.5 0.6 V VIHCK Clock Input High Level 2.4 VCC 3.0 VCC V LOGIC INPUTS/OUTPUTS (D[0:7], A[0:2], IOR#, IOW#/R/W#, CS#, INT/IRQ#, RST#/RST, I/M#, PWRSAVE, ACP, R_EN VIL Input Low Voltage -0.3 0.7 -0.3 0.7 V VIH Input High Voltage 2.0 5.5 2.0 5.5 V VOL Output Low Voltage 0.4 V VOH Output High Voltage 0.4 2.0 2.0 V IIL Input Low Leakage Current +/-10 +/-10 uA IHL Input High Leakage Current +/-10 +/-10 uA +12 V RS-485 INPUTS (RX+, RX-) Input Voltage Range -7 +12 -7 RS-485 OUTPUTS (TX+, TX-) VOD Differential Driver Output RL = 60 ohm VOC Driver Common-Mode Ouput Voltage RL = 60 ohm ILKGR +2 Output Leakage Current 37 +2 V +3 +3 V +/-20 +/-20 uA XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 AC ELECTRICAL CHARACTERISTICS UNLESS OTHERWISE NOTED: TA=-40O TO +85OC, VCC=3.3 OR 5V ± 10%, 70 PF LOAD WHERE APPLICABLE SYMBOL LIMITS 3.3 PARAMETER MIN - LIMITS 5.0 MAX MIN UNIT MAX Crystal Frequency 24 24 MHz OSC External Clock Frequency 64 64 MHz CLK External Clock Low/High Time 30 30 ns TAS Address Setup Time (16 Mode) 0 0 ns TAH Address Hold Time (16 Mode) 0 0 ns TCS Chip Select Width (16 Mode) 65 65 ns TRD IOR# Strobe Width (16 Mode) 65 65 ns TDY Read Cycle Delay (16 Mode) 65 65 ns TRDV Data Access Time (16 Mode) TDD Data Disable Time (16 Mode) 0 TWR IOW# Strobe Width (16 Mode) 65 65 ns TDY Write Cycle Delay (16 Mode) 65 65 ns TDS Data Setup Time (16 Mode) 10 10 ns TDH Data Hold Time (16 Mode) 5 5 ns TADS Address Setup (68 Mode) 0 0 ns TADH Address Hold (68 Mode) 0 0 ns TRWS R/W# Setup to CS# (68 Mode) 0 0 ns TRDA Read Data Access (68 mode) TRDH Read Data Disable Time (68 mode) 0 TWDS Write Data Setup (68 mode) 10 10 ns TWDH Write Data Hold (68 Mode) 5 5 ns TRWH CS# De-asserted to R/W# De-asserted (68 Mode) 5 5 ns TCSL CS# Width (68 Mode) 65 65 ns TCSD CS# Cycle Delay (68 Mode) 65 65 ns TWDO Delay From IOW# To Output 50 50 ns TMOD Delay To Set Interrupt From MODEM Input 50 50 ns TRSI Delay To Reset Interrupt From IOR# 50 50 ns TSSI Delay From Stop To Set Interrupt 1 1 Bclk TRRI Delay From IOR# To Reset Interrupt 50 50 ns 60 15 0 60 38 15 0 60 ns 15 ns 60 ns 15 ns XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 AC ELECTRICAL CHARACTERISTICS UNLESS OTHERWISE NOTED: TA=-40O TO +85OC, VCC=3.3 OR 5V ± 10%, 70 PF LOAD WHERE APPLICABLE SYMBOL LIMITS 3.3 PARAMETER MIN TSI Delay From Stop To Interrupt TINT Delay From Initial INT Reset To Transmit Start TWRI Delay From IOW# To Reset Interrupt TRST Reset Pulse Width 40 N Baud Rate Divisor 1 Bclk LIMITS 5.0 MAX 50 8 24 8 50 Baud Clock CLK CLK EXTERNAL CLOCK OSC 39 50 ns 24 Bclk 50 ns 40 216-1 1 ns 216-1 16X or 8X of data rate FIGURE 12. CLOCK TIMING UNIT MAX MIN Hz XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FIGURE 13. MODEM INPUT/OUTPUT TIMING IOW# T WDO RTS# DTR# Change of state Change of state CD# CTS# DSR# Change of state Change of state T MOD T MOD Activ e INT Activ e Activ e T RSI Activ e IOR# Activ e Activ e T MOD Change of state RI# 40 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FIGURE 14. 16 MODE (INTEL) DATA BUS READ TIMING A0A2 Valid Address Valid Address TAS TAS TAH TCS TAH TCS CS# TDY TRD TRD IOR# TDD TRDV TDD TRDV Valid Data D0-D7 Valid Data RDTm FIGURE 15. 16 MODE (INTEL) DATA BUS WRITE TIMING A0A2 Valid Address Valid Address TAS TAS TAH TCS TAH TCS CS# TDY TWR TWR IOW# TDS D0-D7 TDH Valid Data TDS TDH Valid Data 16Write 41 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FIGURE 16. 68 MODE (MOTOROLA) DATA BUS READ TIMING A0-A2 Valid Address TADS TCSL Valid Address TADH CS# TCSD TRWS TRWH R/W# TRDH TRDA D0-D7 Valid Data Valid Data 68Read FIGURE 17. 68 MODE (MOTOROLA) DATA BUS WRITE TIMING A0-A2 Valid Address TADS TCSL Valid Address TADH CS# TCSD TRWS TRWH R/W# TWDS D0-D7 T WDH Valid Data Valid Data 68Write 42 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FIGURE 18. RECEIVE READY INTERRUPT TIMING [NON-FIFO MODE] RX Start Bit Stop Bit D0:D7 INT D0:D7 D0:D7 TSSR TSSR TSSR 1 Byte in RHR 1 Byte in RHR 1 Byte in RHR TRR TRR TRR IOR# (Reading data out of RHR) RXNFM FIGURE 19. TRANSMIT READY INTERRUPT TIMING [NON-FIFO MODE] TX (Unloading) IER[1] enabled Start Bit Stop Bit D0:D7 ISR is read D0:D7 D0:D7 ISR is read ISR is read INT* TWRI TWRI TSRT TWRI TSRT TSRT IOW# (Loading data into THR) TXNonFIFO *INT is cleared when the ISR is read or when data is loaded into the THR. 43 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 FIGURE 20. RECEIVE READY INTERRUPT TIMING [FIFO MODE] Start Bit RX S D0:D7 S D0:D7 T D0:D7 Stop Bit S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T RX FIFO drops below RX Trigger Level TSSI INT TSSR RX FIFO fills up to RX Trigger Level or RX Data Timeout TRRI IOR# (Reading data out of RX FIFO) RXINTDMA# FIGURE 21. TRANSMIT READY INTERRUPT TIMING [FIFO MODE] TX FIFO Empty TX Start Bit Stop Bit S D0:D7 T IER[1] enabled Last Data Byte Transmitted T S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T TSI ISR is read S D0:D7 T ISR is read INT* TX FIFO fills up to trigger level TWRI TX FIFO drops below trigger level IOW# (Loading data into FIFO) TX INT *INT is cleared when the ISR is read or when TX FIFO fills up to the trigger level. 44 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 MECHANICAL DIMENSIONS TOP VIEW BOTTOM VIEW SIDE VIEW TERMINAL DETAILS Drawing No.: POD-00000041 Revision: B.2 45 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER RECOMMENDED LAND PATTERN AND STENCIL TYPICAL RECOMMENDED LAND PATTERN TYPICAL RECOMMENDED STENCIL Drawing No.: POD-00000041 Revision: B.2 46 REV. 1.0.4 XR19L400 SINGLE CHANNEL INTEGRATED UART AND RS-485 TRANSCEIVER REV. 1.0.4 REVISION HISTORY DATE REVISION DESCRIPTION April 2007 P1.0.0 Preliminary Datasheet June 2007 P1.0.1 Updated pinout. July 2007 1.0.0 Final Datasheet. Updated DC Electrical characteristics. October 2007 1.0.1 Updated maximum crystal frequency and external clock frequency in AC Electrical Characteristics. December 2007 1.0.2 Removed references to the special character detect since that feature is not available in this device. July 2009 1.0.3 Clarified VCC33 and VCC50 pin descriptions. April 2018 1.0.4 Update to MaxLinear logo. Update format and Ordering Information. Corporate Headquarters: High Performance Analog: 5966 La Place Court 1060 Rincon Circle Suite 100 San Jose, CA 95131 Carlsbad, CA 92008  Tel.: +1 (669) 265-6100 Tel.:+1 (760) 692-0711 Fax: +1 (669) 265-6101 Fax: +1 (760) 444-8598 Email: serial techsupport@exar.com www.maxlinear.com www.exar.com The content of this document is furnished for informational use only, is subject to change without notice, and should not be construed as a commitment by MaxLinear, Inc.. 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Products are not authorized for use in such applications unless MaxLinear, Inc. receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of MaxLinear, Inc. is adequately protected under the circumstances. MaxLinear, Inc. may have patents, patent applications, trademarks, copyrights, or other intellectual property rights covering subject matter in this document. Except as expressly provided in any written license agreement from MaxLinear, Inc., the furnishing of this document does not give you any license to these patents, trademarks, copyrights, or other intellectual property. Company and product names may be registered trademarks or trademarks of the respective owners with which they are associated. © 2009 - 2018 MaxLinear, Inc. All rights reserved 47