XR16V2750_0709

XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO SEPTEMBER 2007 REV. 1.0.3 GENERAL DESCRIPTION The XR16V27501 (V2750) is a high performance dual universal asynchronous receiver and transmitter (UART) with 64 byte TX and RX FIFOs. The device operates from 2.25 to 3.6 volts with 5 Volt tolerant inputs and is pin-to-pin compatible to Exar’s ST16C2550 and XR16L2750. The V2750 register set is identical to the XR16L2750 and is compatible to the ST16C2550 and the XR16C2850 enhanced features. It supports the Exar’s enhanced features of programmable FIFO trigger level and FIFO level counters, automatic hardware (RTS/CTS) and software flow control, automatic RS-485 half duplex direction control output and a complete modem interface. Onboard registers provide the user with operational status and data error flags. An internal loopback capability allows system diagnostics. Independent programmable baud rate generators are provided in each channel to select data rates up to 8 Mbps at 3.3 Volt and 8X sampling clock. The V2750 is available in 48-pin TQFP and 32-pin QFN packages. NOTE: 1 Covered by U.S. Patent #5,649,122 FEATURES • 2.25 to 3.6 Volt Operation • 5 Volt Tolerant Inputs • Pin-to-pin compatible to Exar’s XR16L2750 and TI’s TL16C752B in the 48-TQFP package • Two independent UART channels ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Register set compatible to XR16L2750 Data rate of up to 8 Mbps at at 3.3 V, and 6.25 Mbps at 2.5 V with 8X sampling rate Fractional Baud Rate Generator Transmit and Receive FIFOs of 64 bytes Programmable TX and RX FIFO Trigger Levels Transmit and Receive FIFO Level Counters Automatic Hardware (RTS/CTS) Flow Control Selectable Auto RTS Flow Control Hysteresis Automatic Software (Xon/Xoff) Flow Control Automatic RS-485 Half-duplex Direction Control Output via RTS# Wireless Infrared (IrDA 1.0) Encoder/Decoder Automatic sleep mode Full modem interface APPLICATIONS • Portable Appliances • Telecommunication Network Routers • Ethernet Network Routers • Cellular Data Devices • Factory Automation and Process Controls FIGURE 1. XR16V2750 BLOCK DIAGRAM • Device Identification and Revision • Crystal oscillator (up to 24MHz) or external clock (upto 64MHz) input • 48-TQFP and 32-QFN packages * 5 Volt Tolerant Inputs A2:A0 D7:D0 IOR# IOW# CSA# CSB# INTA INTB TXRDYA# TXRDYB# RXRDYA# RXRDYB# Reset 8-bit Data Bus Interface UART Channel A UART Regs BRG 64 Byte TX FIFO TX & RX IR ENDEC 2.25 to 3.6 Volt VCC GND TXA, RXA, DTRA#, DSRA#, RTSA#, DTSA#, CDA#, RIA#, OP2A# 64 Byte RX FIFO TXB, RXB, DTRB#, DSRB#, RTSB#, CTSB#, CDB#, RIB#, OP2B# XTAL1 XTAL2 2750BLK UART Channel B (same as Channel A) Crystal Osc/Buffer Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 2. PIN OUT ASSIGNMENT TXRDYA# DSRA# CTSA# CDA# REV. 1.0.3 VCC RIA# 48 40 38 47 46 44 39 37 45 43 42 41 NC D4 D3 D2 D1 D0 D5 D6 D7 RXB RXA 1 2 3 4 5 36 35 34 33 RESET DTRB# DTRA# RTSA# OP2A# RXRDYA# INTA INTB A0 A1 A2 NC TXRDYB# 6 TXA TXB 7 8 XR16V2750 48-pin TQFP 32 31 30 29 28 27 26 25 OP2B# 9 CSA# 10 CSB# 11 NC 12 15 13 18 19 20 22 16 14 17 21 23 CTSB# 24 NC RXRDYB# DSRB# CDB# XTAL2 GND RIB# D1 31 D4 30 D3 32 D5 29 D2 27 D0 26 28 25 CTSA# VCC RTSB# XTAL1 IOW# IOR# D6 D7 RXB RXA TXA TXB CSA# CSB# 1 2 3 4 5 6 7 8 XTAL2 11 13 CTSB# 16 IOW# 12 IOR# 14 RTSB# 15 XTAL1 10 9 XR16V2750 32-pin QFN 24 23 22 21 20 19 18 17 RESET RTSA# INTA INTB A0 A1 A2 NC ORDERING INFORMATION PART NUMBER XR16V2750IL32 XR16V2750IM PACKAGE 32-pin QFN 48-Lead TQFP OPERATING TEMPERATURE RANGE -40°C to +85°C -40°C to +85°C DEVICE STATUS Active Active 2 GND NC XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO PIN DESCRIPTIONS Pin Description NAME 32-QFN PIN # 48-TQFP PIN # TYPE DESCRIPTION DATA BUS INTERFACE A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 IOR# 18 19 20 2 1 32 31 30 29 28 27 14 26 27 28 3 2 1 48 47 46 45 44 19 I Address data lines [2:0]. These 3 address lines select one of the internal registers in UART channel A/B during a data bus transaction. Data bus lines [7:0] (bidirectional). I/O I Input/Output Read Strobe (active low). The falling edge instigates an internal read cycle and retrieves the data byte from an internal register pointed to by the address lines [A2:A0]. The data byte is placed on the data bus to allow the host processor to read it on the rising edge. Input/Output Write Strobe (active low). The falling edge instigates an internal write cycle and the rising edge transfers the data byte on the data bus to an internal register pointed by the address lines. UART channel A select (active low) to enable UART channel A in the device for data bus operation. UART channel B select (active low) to enable UART channel B in the device for data bus operation. UART channel A Interrupt output. The output state is defined by the user through the software setting of MCR[3]. INTA is set to the active mode and OP2A# output LOW when MCR[3] is set to a logic 1. INTA is set to the three state mode and OP2A# output HIGH when MCR[3] is set to a logic 0 (default). See MCR[3]. UART channel B Interrupt output. The output state is defined by the user through the software setting of MCR[3]. INTB is set to the active mode and OP2B# output LOW when MCR[3] is set to a logic 1. INTB is set to the three state mode and OP2B# output HIGH when MCR[3] is set to a logic 0 (default). See MCR[3]. UART channel A Transmitter Ready (active low). The output provides the TX FIFO/THR status for transmit channel A. See Table 2. If it is not used, leave it unconnected. UART channel A Receiver Ready (active low). This output provides the RX FIFO/RHR status for receive channel A. See Table 2. If it is not used, leave it unconnected. UART channel B Transmitter Ready (active low). The output provides the TX FIFO/THR status for transmit channel B. See Table 3. If it is not used, leave it unconnected. IOW# 12 15 I CSA# CSB# INTA 7 8 22 10 11 30 I I O INTB 21 29 O TXRDYA# - 43 O RXRDYA# - 31 O TXRDYB# - 6 O 3 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO Pin Description NAME RXRDYB# 32-QFN PIN # 48-TQFP PIN # 18 TYPE O DESCRIPTION UART channel B Receiver Ready (active low). This output provides the RX FIFO/RHR status for receive channel B. See Table 2. If it is not used, leave it unconnected. REV. 1.0.3 MODEM OR SERIAL I/O INTERFACE TXA 5 7 O UART channel A Transmit Data or infrared encoder data. Standard transmit and receive interface is enabled when MCR[6] = 0. In this mode, the TX signal will be HIGH during reset or idle (no data). Infrared IrDA transmit and receive interface is enabled when MCR[6] = 1. In the Infrared mode, the inactive state (no data) for the Infrared encoder/ decoder interface is LOW. If it is not used, leave it unconnected. UART channel A Receive Data or infrared receive data. Normal receive data input must idle HIGH. The infrared receiver pulses typically idles at LOW but can be inverted by software control prior going in to the decoder, see MCR[6] and FCTR[2]. If this pin is not used, tie it to VCC or pull it high via a 100k ohm resistor. UART channel A Request-to-Send (active low) or general purpose output. This output must be asserted prior to using auto RTS flow control, see EFR[6], MCR[1], FCTR[1:0], EMSR[5:4] and IER[6]. For auto RS485 half-duplex direction control, see FCTR[3] and EMSR[3]. UART channel A Clear-to-Send (active low) or general purpose input. It can be used for auto CTS flow control, see EFR[7], and IER[7]. This input should be connected to VCC when not used. UART channel A Data-Terminal-Ready (active low) or general purpose output. If it is not used, leave it unconnected. UART channel A Data-Set-Ready (active low) or general purpose input. This input should be connected to VCC when not used. This input has no effect on the UART. UART channel A Carrier-Detect (active low) or general purpose input. This input should be connected to VCC when not used. This input has no effect on the UART. UART channel A Ring-Indicator (active low) or general purpose input. This input should be connected to VCC when not used. This input has no effect on the UART. Output Port 2 Channel A - The output state is defined by the user and through the software setting of MCR[3]. INTA is set to the active mode and OP2A# output LOW when MCR[3] is set to a logic 1. INTA is set to the three state mode and OP2A# output HIGH when MCR[3] is set to a logic 0. See MCR[3]. If INTA is used, this output should not be used as a general output else it will disturb the INTA output functionality. UART channel B Transmit Data or infrared encoder data. Standard transmit and receive interface is enabled when MCR[6] = 0. In this mode, the TX signal will be HIGH during reset or idle (no data). Infrared IrDA transmit and receive interface is enabled when MCR[6] = 1. In the Infrared mode, the inactive state (no data) for the Infrared encoder/ decoder interface is LOW. If it is not used, leave it unconnected. RXA 4 5 I RTSA# 23 33 O CTSA# 25 38 I DTRA# DSRA# - 34 39 O I CDA# - 40 I RIA# - 41 I OP2A# - 32 O TXB 6 8 O 4 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO Pin Description NAME RXB 32-QFN PIN # 3 48-TQFP PIN # 4 TYPE I DESCRIPTION UART channel B Receive Data or infrared receive data. Normal receive data input must idle HIGH. The infrared receiver pulses typically idles at logic 0 but can be inverted by software control prior going in to the decoder, see MCR[6] and FCTR[2]. If this pin is not used, tie it to VCC or pull it high via a 100k ohm resistor. UART channel B Request-to-Send (active low) or general purpose output. This port must be asserted prior to using auto RTS flow control, see EFR[6], MCR[1], FCTR[1:0], EMSR[5:4] and IER[6]. For auto RS485 half-duplex direction control, see FCTR[3] and EMSR[3]. UART channel B Clear-to-Send (active low) or general purpose input. It can be used for auto CTS flow control, see EFR[7], and IER[7]. This input should be connected to VCC when not used. UART channel B Data-Terminal-Ready (active low) or general purpose output. If it is not used, leave it unconnected. UART channel B Data-Set-Ready (active low) or general purpose input. This input should be connected to VCC when not used. This input has no effect on the UART. UART channel B Carrier-Detect (active low) or general purpose input. This input should be connected to VCC when not used. This input has no effect on the UART. UART channel B Ring-Indicator (active low) or general purpose input. This input should be connected to VCC when not used. This input has no effect on the UART. Output Port 2 Channel B - The output state is defined by the user and through the software setting of MCR[3]. INTB is set to the active mode and OP2B# output LOW when MCR[3] is set to a logic 1. INTB is set to the three state mode and OP2B# output HIGH when MCR[3] is set to a logic 0. See MCR[3]. If INTB is used, this output should not be used as a general output else it will disturb the INTB output functionality. RTSB# 15 22 O CTSB# 16 23 I DTRB# DSRB# - 35 20 O I CDB# - 16 I RIB# - 21 I OP2B# - 9 O ANCILLARY SIGNALS XTAL1 XTAL2 RESET 10 11 24 13 14 36 I O I Crystal or external clock input. Caution: this input is not 5V tolerant. Crystal or buffered clock output. Reset (active high) - A longer than 40 ns HIGH pulse on this pin will reset the internal registers and all outputs. The UART transmitter output will be held HIGH, the receiver input will be ignored and outputs are reset during reset period (see Table 16). 2.25V to 3.6V power supply. All input pins, except XTAL1, are 5V tolerant. Power supply common, ground. The center pad on the backside of the 32-QFN package is metallic and should be 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. VCC GND GND 26 13 Center Pad 42 17 N/A Pwr Pwr Pwr 5 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO Pin Description NAME N.C. 32-QFN PIN # 9, 17 48-TQFP PIN # 12, 24, 25, 37 TYPE No Connection. DESCRIPTION REV. 1.0.3 Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain. 6 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 1.0 PRODUCT DESCRIPTION The XR16V2750 (V2750) integrates the functions of 2 enhanced 16C550 Universal Asynchronous Receiver and Transmitter (UART). Each UART is independently controlled having its own set of device configuration registers. The configuration registers set is 16550 UART compatible for control, status and data transfer. Additionally, each UART channel has 64-bytes of transmit and receive FIFOs, automatic RTS/CTS hardware flow control with hysteresis control, automatic Xon/Xoff and special character software flow control, programmable transmit and receive FIFO trigger levels, FIFO level counters, infrared encoder and decoder (IrDA ver 1.0), programmable fractional baud rate generator with a prescaler of divide by 1 or 4, and data rate up to 8 Mbps with 8X sampling clock rate or 4 Mbps in the 16X rate. The XR16V2750 is a 2.25 to 3.6V device with 5 volt tolerant inputs. The V2750 is fabricated with an advanced CMOS process. Enhanced Features The V2750 DUART provides a solution that supports 64 bytes of transmit and receive FIFO memory, instead of 16 bytes in the ST16C2550 or one byte in the ST16C2450. The V2750 is designed to work with low supply voltage and high performance data communication systems, that require fast data processing time. Increased performance is realized in the V2750 by the larger transmit and receive FIFOs, FIFO trigger level control, FIFO level counters and automatic flow control mechanism. This allows the external processor to handle more networking tasks within a given time. For example, the ST16C2550 with a 16 byte FIFO, unloads 16 bytes of receive data in 1.53 ms (This example uses a character length of 11 bits, including start/stop bits at 115.2 Kbps). This means the external CPU will have to service the receive FIFO at 1.53 ms intervals. However with the 64 byte FIFO in the V2750, the data buffer will not require unloading/loading for 6.1 ms. 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 programmable FIFO level trigger interrupt and automatic hardware/ software flow control is uniquely provided for maximum data throughput performance especially when operating in a multi-channel system. The combination of the above greatly reduces the CPU’s bandwidth requirement, increases performance, and reduces power consumption. The V2750 supports a half-duplex output direction control signaling pin, RTS# A/B, to enable and disable the external RS-485 transceiver operation. It automatically switches the logic state of the output pin to the receive state after the last stop-bit of the last character has been shifted out of the transmitter. After receiving, the logic state of the output pin switches back to the transmit state when a data byte is loaded in the transmitter. The auto RS-485 direction control pin is not activated after reset. To activate the direction control function, user has to set FCTR Bit-3 to “1”. This pin is normally high for receive state, low for transmit state. Data Rate The V2750 is capable of operation up to 4 Mbps at 3.3V with 16X internal sampling clock rate and 8 Mbps at 3.3V with 8X sampling clock rate. The device can operate with an external 24 MHz crystal at 2.5V on pins XTAL1 and XTAL2, or external clock source of up to 64 MHz on XTAL1 pin. With a typical crystal of 14.7456 MHz and through a software option, the user can set the prescaler bit for data rates of up to 1.84 Mbps. The rich feature set of the V2750 is available through the internal registers. Automatic hardware/software flow control, selectable transmit and receive FIFO trigger levels, selectable TX and RX baud rates, infrared encoder/decoder interface, modem interface controls, and a sleep mode are all standard features. Following a power on reset or an external reset, the V2750 is software compatible with previous generation of UARTs, 16C450, 16C550 and 16C650A as well as the 16C850. 7 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 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 V2750 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# signals. Both UART channels share the same data bus for host operations. The data bus interconnections are shown in Figure 3. FIGURE 3. XR16V2750 DATA BUS INTERCONNECTIONS REV. 1.0.3 D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 IOR# IOW# UART_CSA# UART_CSB# UART_INTA UART_INTB TXRDYA# RXRDYA# TXRDYB# RXRDYB# UART_RESET D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 IOR# IOW# CSA# CSB# INTA INTB TXRDYA# RXRDYA# TXRDYB# RXRDYB# RESET VCC TXA RXA DTRA# RTSA# CTSA# DSRA# CDA# RIA# OP2A# VCC UART Channel A Serial Interface of RS-232, RS-485 TXB RXB UART Channel B DTRB# RTSB# CTSB# DSRB# CDB# RIB# OP2B# Serial Interface of RS-232, RS-485 GND 2750int 2.2 5-Volt Tolerant Inputs The V2750 can accept up to 5V inputs even when operating at 3.3V or 2.5V. But note that if the V2750 is operating at 2.5V, its VOH may not be high enough to meet the requirements of the VIH of a CPU or a serial transceiver that is operating at 5V. Caution: XTAL1 is not 5 volt tolerant. 2.3 Device Reset The RESET input resets the internal registers and the serial interface outputs in both channels to their default state (see Table 16). An active high 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 XR16V2750 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 (DLD = 0xXX). Now reading the content of the DLM will provide 0x0A for the XR16V2750 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 A and B Selection The UART provides the user with the capability to bi-directionally transfer information between an external CPU and an external serial communication device. A LOW signal on the chip select pins, CSA# or CSB#, allows the user to select UART channel A or B to configure, send transmit data and/or unload receive data to/ from the UART. Selecting both UARTs can be useful during power up initialization to write to the same internal 8 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO registers, but do not attempt to read from both uarts simultaneously. Individual channel select functions are shown in Table 1. TABLE 1: CHANNEL A AND B SELECT CSA# 1 0 1 0 CSB# 1 1 0 0 FUNCTION UART de-selected Channel A selected Channel B selected Channel A and B selected 2.6 Channel A and B Internal Registers Each UART channel in the V2750 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/DLD), and a user accessible Scratchpad Register (SPR). Beyond the general 16C2550 features and capabilities, the V2750 offers enhanced feature registers (EMSR, FLVL, EFR, Xon/Xoff 1, Xon/Xoff 2, FCTR, TRG, FC) that provide automatic RTS and CTS hardware flow control, Xon/Xoff software flow control, automatic RS-485 half-duplex direction output enable/disable, 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 22. 2.7 DMA Mode The device does not support direct memory access. The DMA Mode (a legacy term) in this document doesn’t mean “direct memory access” but refers to data block transfer operation. The DMA mode affects the state of the RXRDY# A/B and TXRDY# A/B output pins. The transmit and receive FIFO trigger levels provide additional flexibility to the user for block mode operation. The LSR bits 5-6 provide an indication when the transmitter is empty or has an empty location(s) for more data. The user can optionally operate the transmit and receive FIFO in the DMA mode (FCR bit-3=1). When the transmit and receive FIFO are enabled and the DMA mode is disabled (FCR bit-3 = 0), the V2750 is placed in single-character mode for data transmit or receive operation. When DMA mode is enabled (FCR bit-3 = 1), the user takes advantage of block mode operation by loading or unloading the FIFO in a block sequence determined by the programmed trigger level. In this mode, the V2750 sets the TXRDY# pin when the transmit FIFO becomes full, and sets the RXRDY# pin when the receive FIFO becomes empty. The following table shows their behavior. Also see Figures 17 through 22. TABLE 2: TXRDY# AND RXRDY# OUTPUTS IN FIFO AND DMA MODE PINS FCR BIT-0=0 (FIFO DISABLED) FCR BIT-0=1 (FIFO ENABLED) FCR Bit-3 = 0 (DMA Mode Disabled) RXRDY# A/B LOW = 1 byte. HIGH = no data. LOW = at least 1 byte in FIFO. HIGH = FIFO empty. FCR Bit-3 = 1 (DMA Mode Enabled) HIGH to LOW transition when FIFO reaches the trigger level, or time-out occurs. LOW to HIGH transition when FIFO empties. LOW = FIFO has at least 1 empty location. HIGH = FIFO is full. TXRDY# A/B LOW = THR empty. LOW = FIFO empty. HIGH = byte in THR. HIGH = at least 1 byte in FIFO. 9 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.8 INTA and INTB Outputs REV. 1.0.3 The INTA and INTB interrupt output changes according to the operating mode and enhanced features setup. Table 3 and 4 summarize the operating behavior for the transmitter and receiver. Also see Figures 17 through 22. TABLE 3: INTA AND INTB PINS OPERATION FOR TRANSMITTER Auto RS485 Mode INTA/B Pin NO FCR BIT-0 = 0 (FIFO DISABLED) LOW = a byte in THR HIGH = THR empty LOW = a byte in THR HIGH = transmitter empty FCR BIT-0 = 1 (FIFO ENABLED) LOW = FIFO above trigger level HIGH = FIFO below trigger level or FIFO empty LOW = FIFO above trigger level HIGH = FIFO below trigger level or transmitter empty INTA/B Pin YES TABLE 4: INTA AND INTB PIN OPERATION FOR RECEIVER FCR BIT-0 = 0 (FIFO DISABLED) INTA/B Pin LOW = no data HIGH = 1 byte FCR BIT-0 = 1 (FIFO ENABLED) LOW = FIFO below trigger level HIGH = FIFO above trigger level 2.9 Crystal Oscillator or External Clock Input The V2750 includes an on-chip oscillator (XTAL1 and XTAL2) to produce a clock for both UART sections in the device. 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 buffer input with XTAL2 pin being the output. Please note that the input XTAL1 is not 5V tolerant and so the maximum at the pin should be VCC. For programming details, see ““Section 2.10, Programmable Baud Rate Generator with Fractional Divisor” on page 11.” FIGURE 4. TYPICAL OSCILLATOR CONNECTIONS XTAL1 XTAL2 R1 0-120 Ω (Optional) R2 500 ΚΩ − 1 ΜΩ Y1 C1 22-47 pF C2 22-47 pF 1.8432 MHz to 24 MHz 10 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 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 100 ppm frequency tolerance) connected externally between the XTAL1 and XTAL2 pins (see Figure 4). The programmable Baud Rate Generator is capable of operating with a crystal oscillator frequency of up to 24 MHz at 2.5V. However, with an external clock input on XTAL1 pin, it can extend its operation up to 64 MHz (8 Mbps serial data rate) at 3.3V with an 8X sampling rate. For further reading on the oscillator circuit please see the Application Note DAN108 on the EXAR web site at http://www.exar.com. 2.10 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 5 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 5. At 8X sampling rate, these data rates would double. Also, when using 8X sampling mode, please note that the bittime 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 V2750 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. 11 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 5. BAUD RATE GENERATOR To Other Channel REV. 1.0.3 DLL, DLM and DLD Registers Prescaler Divide by 1 XTAL1 XTAL2 Crystal Osc/ Buffer Prescaler Divide by 4 MCR Bit-7=0 (default) Fractional Baud Rate Generator Logic MCR Bit-7=1 16X or 8X Sampling Rate Clock to Transmitter and Receiver TABLE 5: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING Required Output Data Rate 400 2400 4800 9600 10000 19200 25000 28800 38400 50000 57600 75000 100000 115200 153600 200000 225000 230400 250000 300000 400000 460800 500000 750000 921600 1000000 DIVISOR FOR 16x Clock (Decimal) 3750 625 312.5 156.25 150 78.125 60 52.0833 39.0625 30 26.0417 20 15 13.0208 9.7656 7.5 6.6667 6.5104 6 5 3.75 3.2552 3 2 1.6276 1.5 DIVISOR OBTAINABLE IN V2750 3750 625 312 8/16 156 4/16 150 78 2/16 60 52 1/16 39 1/16 30 26 1/16 20 15 13 9 12/16 7 8/16 6 11/16 6 8/16 6 5 3 12/16 3 4/16 3 2 1 10/16 1 8/16 DLM PROGRAM VALUE (HEX) E 2 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 DLL PROGRAM VALUE (HEX) A6 71 38 9C 96 4E 3C 34 27 1E 1A 14 F D 9 7 6 6 6 5 3 3 3 2 1 1 DLD PROGRAM VALUE (HEX) 0 0 8 4 0 2 0 1 1 0 1 0 0 0 C 8 B 8 0 0 C 4 0 0 A 8 DATA ERROR RATE (%) 0 0 0 0 0 0 0 0.04 0 0 0.08 0 0 0.16 0.16 0 0.31 0.16 0 0 0 0.16 0 0 0.16 0 12 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.11 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). 2.11.1 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. 2.11.2 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. FIGURE 6. TRANSMITTER OPERATION IN NON-FIFO MODE Data Byte Transmit Holding Register (THR) THR Interrupt (ISR bit-1) Enabled by IER bit-1 16X or 8X Clock (EMSR Bit-7) Transmit Shift Register (TSR) M S B L S B TXNOFIFO1 2.11.3 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 TSR flag (LSR bit-6) is set when TSR/FIFO becomes empty. 13 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 7. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE REV. 1.0.3 Transmit Data Byte Transm it 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 Auto CTS Flow Control (CTS# pin) Flow Control Characters (Xoff1/2 and Xon1/2 Reg. Auto Software Flow Control 16X or 8X Clock (EMSR bit-7) T ransm it Data Shift Register (TSR) T XF IF O 1 2.12 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. 2.12.1 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. 14 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 8. RECEIVER OPERATION IN NON-FIFO MODE 1 6 X o r 8 X C lo ck (E M S R b it-7 ) R e ce ive D a ta S hift R e giste r (R S R ) D ata B it V alid a tio n R e ce ive D a ta C h a ra cte rs R ece ive D a ta B yte a n d E rro rs E rro r T a g s in LS R b its 4 :2 R e ce ive D a ta H o ldin g R e g ister (R H R ) R H R Inte rru pt (IS R b it-2 ) R X F IF O 1 FIGURE 9. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE 16X or 8X Clock (EMSR bit-7) Receive Data Shift Register (RSR) Data Bit Validation Receive Data Characters 64 bytes by 11-bit wide FIFO Error Tags (64-sets) Example - :RX FIFO trigger level selected at 16 bytes (See Note Below) Data falls to RTS# re-asserts when data falls below the flow 8 control trigger level to restart remote transmitter. Receive Data FIFO Enable by EFR bit-6=1, MCR bit-1. FIFO Trigger=16 RHR Interrupt (ISR bit-2) programmed for desired FIFO trigger level. FIFO is Enabled by FCR bit-0=1 RTS# de-asserts when data fills above the flow control trigger level to suspend remote transmitter. Enable by EFR bit-6=1, MCR bit-1. Data fills to 24 Error Tags in LSR bits 4:2 Receive Data Byte and Errors Receive Data RXFIFO1 NOTE: Table-B selected as Trigger Table for Figure 9 (Table 10). 15 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.13 Auto RTS (Hardware) Flow Control REV. 1.0.3 Automatic RTS hardware flow control is used to prevent data overrun to the local receiver FIFO. The RTS# output is used to request remote unit to suspend/resume data transmission. The auto RTS flow control features is enabled to fit specific application requirement (see Figure 10): • Enable auto RTS flow control using EFR bit-6. • The auto RTS function must be started by asserting RTS# output pin (MCR bit-1 to logic 1 after it is enabled). If using the Auto RTS interrupt: • Enable RTS interrupt through IER bit-6 (after setting EFR bit-4). The UART issues an interrupt when the RTS# pin makes a transition from low to high: ISR bit-5 will be set to logic 1. 2.14 Auto RTS Hysteresis The V2750 has a new feature that provides flow control trigger hysteresis while maintaining compatibility with the XR16C850, ST16C650A and ST16C550 family of UARTs. With the Auto RTS function enabled, an interrupt is generated when the receive FIFO reaches the programmed RX trigger level. The RTS# pin will not be forced HIGH (RTS off) until the receive FIFO reaches the upper limit of the hysteresis level. The RTS# pin will return LOW after the RX FIFO is unloaded to the lower limit of the hysteresis level. Under the above described conditions, the V2750 will continue to accept data until the receive FIFO gets full. The Auto RTS function is initiated when the RTS# output pin is asserted LOW (RTS On). Table 13 shows the complete details for the Auto RTS# Hysteresis levels. Please note that this table is for programmable trigger levels only (Table D). The hysteresis values for Tables A-C are the next higher and next lower trigger levels in the corresponding table. 2.15 Auto CTS Flow Control Automatic CTS flow control is used to prevent data overrun to the remote receiver FIFO. The CTS# input is monitored to suspend/restart the local transmitter. The auto CTS flow control feature is selected to fit specific application requirement (see Figure 10): • Enable auto CTS flow control using EFR bit-7. If using the Auto CTS interrupt: • Enable CTS interrupt through IER bit-7 (after setting EFR bit-4). The UART issues an interrupt when the CTS# pin is de-asserted (HIGH): ISR bit-5 will be set to 1, and UART will suspend transmission as soon as the stop bit of the character in process is shifted out. Transmission is resumed after the CTS# input is reasserted (LOW), indicating more data may be sent. 16 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 10. AUTO RTS AND CTS FLOW CONTROL OPERATION Local UART UARTA Receiver FIFO Trigger Reached Auto RTS Trigger Level Transmitter Auto CTS Monitor RXA TXB Remote UART UARTB Transmitter Auto CTS Monitor Receiver FIFO Trigger Reached Auto RTS Trigger Level RTSA# TXA CTSB# RXB CTSA# Assert RTS# to Begin Transmission 1 ON 2 7 ON 3 8 OFF RTSB# RTSA# CTSB# TXB OFF 10 11 ON ON Data Starts 4 RXA FIFO INTA (RXA FIFO Interrupt) Receive RX FIFO Data Trigger Level 5 6 Suspend Restart 9 RTS High Threshold RTS Low Threshold 12 RX FIFO Trigger Level RTSCTS1 The local UART (UARTA) starts data transfer by asserting RTSA# (1). RTSA# is normally connected to CTSB# (2) of remote UART (UARTB). CTSB# allows its transmitter to send data (3). TXB data arrives and fills UARTA receive FIFO (4). When RXA data fills up to its receive FIFO trigger level, UARTA activates its RXA data ready interrupt (5) and continues to receive and put data into its FIFO. If interrupt service latency is long and data is not being unloaded, UARTA monitors its receive data fill level to match the upper threshold of RTS delay and de-assert RTSA# (6). CTSB# follows (7) and request UARTB transmitter to suspend data transfer. UARTB stops or finishes sending the data bits in its transmit shift register (8). When receive FIFO data in UARTA is unloaded to match the lower threshold of RTS delay (9), UARTA re-asserts RTSA# (10), CTSB# recognizes the change (11) and restarts its transmitter and data flow again until next receive FIFO trigger (12). This same event applies to the reverse direction when UARTA sends data to UARTB with RTSB# and CTSA# controlling the data flow. 17 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.16 Auto Xon/Xoff (Software) Flow Control REV. 1.0.3 When software flow control is enabled (See Table 15), the V2750 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 V2750 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 V2750 will monitor the receive data stream for a match to the Xon-1,2 character. If a match is found, the V2750 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 0x00. 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 15) and suspend/resume transmissions. When double 8-bit Xon/Xoff characters are selected, the V2750 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 V2750 automatically sends an Xoff message via the serial TX output to the remote modem. The V2750 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). To clear this condition, the V2750 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 trigger level minus the hysteresis value (for Trigger Table D). This hysteresis value is the same as the Auto RTS Hysteresis value in Table 14. Table 6 below explains this when Trigger Table-B (See Table 10) is selected. TABLE 6: AUTO XON/XOFF (SOFTWARE) FLOW CONTROL RX TRIGGER LEVEL 8 16 24 28 INT PIN ACTIVATION 8 16 24 28 XOFF CHARACTER(S) SENT (CHARACTERS IN RX FIFO) 8* 16* 24* 28* XON CHARACTER(S) SENT (CHARACTERS IN RX FIFO) 0 8 16 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 10-bit word length setting. 2.17 Special Character Detect A special character detect feature is provided to detect an 8-bit character when bit-5 is set in the Enhanced Feature Register (EFR). When this character (Xoff2) is detected, it will be placed in the FIFO along with normal incoming RX data. The V2750 compares each incoming receive character with Xoff-2 data. If a match exists, the received data will be transferred to FIFO and ISR bit-4 will be set to indicate detection of special character. Although the Internal Register Table shows Xon, Xoff Registers with eight bits of character information, the actual number of bits is dependent on the programmed word length. Line Control Register (LCR) bits 0-1 defines the number of character bits, i.e., either 5 bits, 6 bits, 7 bits, or 8 bits. The word length selected by LCR bits 0-1 also determines the number of bits that will be used for the special character comparison. 2.18 Auto RS485 Half-duplex Control The auto RS485 half-duplex direction control changes the behavior of the transmitter when enabled by FCTR bit-3. By default, it de-asserts RTS# (HIGH) output following the last stop bit of the last character that has been transmitted. This helps in turning around the transceiver to receive the remote station’s response. When the host is ready to transmit next polling data packet again, it only has to load data bytes to the transmit FIFO. The transmitter automatically re-asserts RTS# (LOW) output prior to sending the data. The RS485 half-duplex direction control output can be inverted by enabling EMSR bit-3. 18 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.19 Infrared Mode The V2750 UART includes the infrared encoder and decoder compatible to the IrDA (Infrared Data Association) version 1.0. The IrDA 1.0 standard that stipulates the infrared encoder sends out a 3/16 of a bit wide HIGH-pulse for each “0” bit in the transmit data stream. This signal encoding reduces the on-time of the infrared LED, hence reduces the power consumption. See Figure 11 below. The infrared encoder and decoder are enabled by setting MCR register bit-6 to a ‘1’. When the infrared feature is enabled, the transmit data output, TX, idles at logic zero level. Likewise, the RX input assumes an idle level of logic zero from a reset and power up, see Figure 11. Typically, the wireless infrared decoder receives the input pulse from the infrared sensing diode on the RX pin. Each time it senses a light pulse, it returns a logic 1 to the data bit stream. However, this is not true with some infrared modules on the market which indicate a logic 0 by a light pulse. So the V2750 has a provision to invert the input polarity to accommodate this. In this case user can enable FCTR bit-2 to invert the input signal. FIGURE 11. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING Character Start Data Bits 1 0 1 0 0 1 1 0 Stop 1 1/2 Bit Time 3/16 Bit Time IrEncoder-1 TX Data 0 Transmit IR Pulse (TX Pin) Bit Time Receive IR Pulse (RX pin) Bit Time 1/16 Clock Delay RX Data 0 Start 1 0 1 0 0 11 0 1 Stop IRdecoder- Data Bits Character 19 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.20 Sleep Mode with Auto Wake-Up REV. 1.0.3 The V2750 supports low voltage system designs, hence, a sleep mode is included to reduce its power consumption when the chip is not actively used. All of these conditions must be satisfied for the V2750 to enter sleep mode: ■ ■ ■ ■ no interrupts pending for both channels of the V2750 (ISR bit-0 = 1) sleep mode of both channels are enabled (IER bit-4 = 1) modem inputs are not toggling (MSR bits 0-3 = 0) RX input pins are idling HIGH The V2750 stops its crystal oscillator to conserve power in the sleep mode. User can check the XTAL2 pin for no clock output as an indication that the device has entered the sleep mode. The V2750 resumes normal operation by any of the following: ■ ■ ■ a receive data start bit transition (HIGH to LOW) 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: CTS#, DSR#, CD#, RI# If the V2750 is awakened by any one of the above conditions, it will return to the sleep mode automatically after all interrupting conditions have been serviced and cleared. If the V2750 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 from channel A or B. The V2750 will stay in the sleep mode of operation until it is disabled by setting IER bit-4 to a logic 0. If the address lines, data bus lines, IOW#, IOR#, CSA#, CSB#, and modem input lines remain steady when the V2750 is in sleep mode, the maximum current will be in the microamp range as specified in the DC Electrical Characteristics on page 41. If the input lines are floating or are toggling while the V2750 is in sleep mode, the current can be up to 100 times more. If any of those signals are toggling or floating, then an external buffer would be required to keep the address, data and control lines steady to achieve the low current. As an alternative, please refer to the XR16L2751 which is pin-to-pin and software compatible with the V2750 but with (some additional pins and) the PowerSave feature that eliminates any unnecessary external buffer. A word of caution: owing to the starting up delay of the crystal oscillator after waking up from sleep mode, 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. Also, it is important to keep RX A/B inputs idling HIGH or “marking” condition during sleep mode to avoid receiving a “break” condition upon the restart. This may occur when the external interface transceivers (RS-232, RS-485 or another type) are also put to sleep mode and cannot maintain the “marking” condition. To avoid this, the designer can use a 47k-100k ohm pull-up resistor on the RXA and RXB pins. 20 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO Internal Loopback 2.21 The V2750 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 12 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. The TX, RTS# and DTR# pins are held while the CTS#, DSR# CD# and RI# inputs are ignored. Caution: the RX input pin must be held HIGH during loopback test else upon exiting the loopback test the UART may detect and report a false “break” signal. Also, Auto RTS/CTS flow control is not supported during internal loopback. FIGURE 12. INTERNAL LOOPBACK IN CHANNEL A AND B VCC Transmit Shift Register (THR/FIFO) MCR bit-4=1 Internal Data Bus Lines and Control Signals Receive Shift Register (RHR/FIFO) VCC RTS# Modem / General Purpose Control Logic RTSA#/RTSB# TXA/TXB RXA/RXB CTS# VCC DTR# CTSA#/CTSB# DTRA#/DTRB# DSR# OP1# RI# VCC OP2# DSRA#/DSRB# RIA#/RIB# OP2A#/OP2B# CD# CDA#/CDB# 21 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 3.0 UART INTERNAL REGISTERS Each of the UART channel in the V2750 has its own set of configuration registers selected by address lines A0, A1 and A2 with CSA# or CSB# selecting the channel. The complete register set is shown on Table 7 and Table 8. TABLE 7: UART INTERNAL REGISTERS ADDRESSES A2 A1 A0 REGISTER 16C550 COMPATIBLE REGISTERS 0 00 RHR - Receive Holding Register THR - Transmit Holding Register DLL - Divisor LSB DLM - Divisor MSB DLD - Divisor Fractional DREV - Device Revision Code DVID - Device Identification Code IER - Interrupt Enable Register ISR - Interrupt Status Register FCR - FIFO Control Register LCR - Line Control Register MCR - Modem Control Register LSR - Line Status Register MSR - Modem Status Register SPR - Scratch Pad Register FLVL - RX/TX FIFO Level Counter Register EMSR - Enhanced Mode Select Register ENHANCED REGISTERS 0 00 TRG - RX/TX FIFO Trigger Level Register FC - RX/TX FIFO Level Counter Register FCTR - Feature Control Register EFR - Enhanced Function Register Xon-1 - Xon Character 1 Xon-2 - Xon Character 2 Xoff-1 - Xoff Character 1 Xoff-2 - Xoff Character 2 Write-only Read-only Read/Write Read/Write Read/Write Read/Write Read/Write Read/Write LCR = 0xBF Read-only Write-only Read/Write Read/Write Read/Write Read-only Read-only Read/Write Read-only Write-only Read/Write Read/Write Read-only Read-only Read/Write Read-only Write-only LCR ≠ 0xBF, FCTR[6] = 0 LCR ≠ 0xBF, FCTR[6] = 1 LCR ≠ 0xBF LCR[7] = 1, LCR ≠ 0xBF, EFR[4] = 1 DLL, DLM = 0x00, LCR[7] = 1, LCR ≠ 0xBF LCR[7] = 0 LCR ≠ 0xBF LCR[7] = 0 READ/WRITE COMMENTS REV. 1.0.3 0 0 0 0 0 0 0 00 01 10 00 01 01 10 LCR[7] = 1, LCR ≠ 0xBF 0 1 1 1 1 1 1 11 00 01 10 11 11 11 0 0 1 1 1 1 01 10 00 01 10 11 22 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO . TABLE 8: INTERNAL REGISTERS DESCRIPTION. 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 000 000 001 RHR THR IER RD WR RD/WR Bit-7 Bit-7 0/ Bit-6 Bit-6 0/ Bit-5 Bit-5 0/ Xoff Int. Enable Bit-4 Bit-4 0/ Sleep Mode Enable Bit-3 Bit-3 Bit-2 Bit-2 Bit-1 Bit-1 Bit-0 Bit-0 LCR[7]=0 CTS Int. RTS Int. Enable Enable Modem RX Line TX RX Stat. Int. Stat. Empty Data Enable Int. Int Int. Enable Enable Enable 010 ISR RD FIFOs FIFOs Enabled Enabled 0/ INT Source Bit-5 0/ 0/ INT Source Bit-4 0/ INT Source Bit-3 INT INT INT Source Source Source Bit-2 Bit-1 Bit-0 LCR ≠ 0xBF 010 FCR WR RX FIFO RX FIFO Trigger Trigger TX FIFO TX FIFO Trigger Trigger DMA Mode Enable TX FIFO Reset RX FIFO Reset FIFOs Enable 011 LCR RD/WR Divisor Enable Set TX Break Set Parity Even Parity Parity Enable Stop Bits Word Word Length Length Bit-1 Bit-0 100 MCR RD/WR 0/ BRG Prescaler Internal OP2#/INT Rsrvd RTS# DTR# Lopback Output (OP1#) Output Output IR Mode XonAny Enable Enable Control Control ENable 0/ 0/ 101 LSR RD RX FIFO Global Error CD# Input Bit-7 THR & TSR Empty RI# Input Bit-6 THR Empty RX Break RX Framing Error RX Parity Error Delta RI# Bit-2 RX Overrun Error Delta DSR# Bit-1 RX Data Ready Delta CTS# Bit-0 LCR ≠ 0xBF 110 111 MSR SPR RD RD/WR DSR# Input Bit-5 CTS# Input Bit-4 Delta CD# Bit-3 LCR ≠ 0xBF FCTR[6]=0 111 EMSR WR 16X Sampling Rate Mode LSR Error Interrupt. Imd/Dly# Auto RTS Hyst. bit-3 Auto RTS Hyst. bit-2 Auto RS485 Output Inversion Rsrvd Rx/Tx FIFO Count Rx/Tx FIFO Count LCR ≠ 0xBF FCTR[6]=1 111 FLVL RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 23 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO TABLE 8: INTERNAL REGISTERS DESCRIPTION. 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 REV. 1.0.3 Baud Rate Generator Divisor 000 001 010 DLL DLM DLD RD/WR RD/WR RD/WR Bit-7 Bit-7 0 Bit-6 Bit-6 0 Bit-5 Bit-5 0 Bit-4 Bit-4 0 Bit-3 Bit-3 Bit-3 Bit-2 Bit-2 Bit-2 Bit-1 Bit-1 Bit-1 Bit-0 Bit-0 Bit-0 LCR[7]=1 LCR ≠ 0xBF LCR[7]=1 LCR ≠ 0xBF EFR[4] = 1 LCR[7]=1 LCR ≠ 0xBF DLL=0x00 DLM=0x00 000 001 DREV DVID RD RD Bit-7 0 Bit-6 0 Bit-5 0 Bit-4 0 Bit-3 1 Bit-2 0 Bit-1 1 Bit-0 0 Enhanced Registers 000 000 001 TRG FC WR RD Bit-7 Bit-7 RX/TX Mode Bit-6 Bit-6 SCPAD Swap Bit-5 Bit-5 Trig Table Bit-1 Special Char Select Bit-4 Bit-4 Trig Table Bit-0 Enable IER [7:4], ISR [5:4], FCR[5:4], MCR[7:5], DLD Bit-3 Bit-3 Auto RS485 Direction Control Software Flow Cntl Bit-3 Bit-3 Bit-3 Bit-3 Bit-3 Bit-2 Bit-2 RX IR Input Inv. Bit-1 Bit-1 Auto RTS Hyst Bit-1 Software Flow Cntl Bit-1 Bit-1 Bit-1 Bit-1 Bit-1 Bit-0 Bit-0 Auto RTS Hyst Bit-0 Software Flow Cntl Bit-0 Bit-0 Bit-0 Bit-0 Bit-0 FCTR RD/WR 010 EFR RD/WR Auto CTS Enable Auto RTS Enable Software Flow Cntl Bit-2 Bit-2 Bit-2 Bit-2 Bit-2 LCR=0XBF 100 101 110 111 XON1 RD/WR XON2 RD/WR XOFF1 RD/WR XOFF2 RD/WR Bit-7 Bit-7 Bit-7 Bit-7 Bit-6 Bit-6 Bit-6 Bit-6 Bit-5 Bit-5 Bit-5 Bit-5 Bit-4 Bit-4 Bit-4 Bit-4 4.0 INTERNAL REGISTER DESCRIPTIONS 4.1 4.2 4.3 Receive Holding Register (RHR) - Read- Only Transmit Holding Register (THR) - Write-Only Interrupt Enable Register (IER) - Read/Write SEE”RECEIVER” ON PAGE 14. SEE”TRANSMITTER” ON PAGE 13. 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). 24 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO IER versus Receive FIFO Interrupt Mode Operation 4.3.1 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 XR16V2750 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. 25 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO IER[4]: Sleep Mode Enable (requires EFR bit-4 = 1) REV. 1.0.3 • 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 receive Xoff interrupt. See Software Flow Control section for details. IER[6]: RTS# Output Interrupt Enable (requires EFR bit-4=1) • Logic 0 = Disable the RTS# interrupt (default). • Logic 1 = Enable the RTS# interrupt. The UART issues an interrupt when the RTS# pin makes a transition from low to high. IER[7]: CTS# Input Interrupt Enable (requires EFR bit-4=1) • Logic 0 = Disable the CTS# interrupt (default). • Logic 1 = Enable the CTS# interrupt. The UART issues an interrupt when CTS# pin makes a transition from low to high. 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 9, 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 RS-485 control). • MSR is by any of the MSR bits 0, 1, 2 and 3. • Receive Xoff/Special character is by detection of a Xoff or Special character. • CTS# is when its transmitter toggles the input pin (from LOW to HIGH) during auto CTS flow control. • RTS# is when its receiver toggles the output pin (from LOW to HIGH) during auto RTS flow control. 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. • Special character interrupt is cleared by a read to ISR or after the next character is received. • RTS# and CTS# flow control interrupts are cleared by a read to the MSR register. 26 XR16V2750 REV. 1.0.3 ] HIGH PERFORMANCE DUART WITH 64-BYTE FIFO TABLE 9: INTERRUPT SOURCE AND PRIORITY LEVEL PRIORITY LEVEL 1 2 3 4 5 6 7 BIT-5 0 0 0 0 0 0 1 0 ISR REGISTER STATUS BITS BIT-4 0 0 0 0 0 1 0 0 BIT-3 0 1 0 0 0 0 0 0 BIT-2 1 1 1 0 0 0 0 0 BIT-1 1 0 0 1 0 0 0 0 BIT-0 0 0 0 0 0 0 0 1 SOURCE OF INTERRUPT LSR (Receiver Line Status Register) RXRDY (Receive Data Time-out) RXRDY (Received Data Ready) TXRDY (Transmit Ready) MSR (Modem Status Register) RXRDY (Received Xoff or Special character) CTS#, RTS# change of state None (default) 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). ISR[3:1]: Interrupt Status These bits indicate the source for a pending interrupt at interrupt priority levels (See Interrupt Source Table 9). ISR[4]: Xoff/Xon or Special Character Interrupt Status This bit is set when EFR[4] = 1 and IER[5] = 1. ISR bit-4 indicates that the receiver detected a data match of the Xoff character(s). If this is an Xoff interrupt, it can be cleared by a read to the ISR. If it is a special character interrupt, it can be cleared by reading ISR or it will automatically clear after the next character received. ISR[5]: RTS#/CTS# Interrupt Status This bit is enabled when EFR[4] = 1. ISR bit-5 indicates that the CTS# or RTS# has been de-asserted. 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, set the transmit/receive FIFO trigger levels, and select the DMA mode. The DMA, and FIFO modes are defined as follows: 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. 27 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FCR[2]: TX FIFO Reset This bit is only active when FCR bit-0 is a ‘1’. REV. 1.0.3 • 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]: DMA Mode Select Controls the behavior of the TXRDY# and RXRDY# pins. See DMA operation section for details. • Logic 0 = Normal Operation (default). • Logic 1 = DMA Mode. 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 10 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 10 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. 28 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION TRIGGER TABLE Table-A FCTR BIT-5 0 FCTR BIT-4 0 FCR BIT-7 FCR BIT-6 FCR BIT-5 0 FCR BIT-4 0 RECEIVE TRIGGER LEVEL TRANSMIT TRIGGER LEVEL 1 (default) COMPATIBILITY 16C550, 16C2550, 16C2552, 16C554, 16C580 0 0 1 1 Table-B 0 1 0 1 0 1 0 0 1 1 0 1 0 1 1 (default) 4 8 14 16 8 24 30 8 16 24 28 0 0 1 1 0 1 0 1 8 16 56 60 X X 8 16 32 56 16C650A 0 0 1 1 Table-C 1 0 0 1 0 1 16C654 0 0 1 1 Table-D 1 1 X 0 1 0 1 X Programmable Programmable 16L2752, 16C2850, 16C2852, 16C850, via TRG via TRG 16C854, 16C864 register. register. FCTR[7] = 0. FCTR[7] = 1. 4.6 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 0 0 1 1 BIT-0 0 1 0 1 WORD LENGTH 5 (default) 6 7 8 29 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 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. REV. 1.0.3 BIT-2 0 1 1 WORD LENGTH STOP BIT LENGTH (BIT TIME(S)) 1 (default) 1-1/2 2 5,6,7,8 5 6,7,8 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 11 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 11: PARITY SELECTION LCR BIT-5 LCR BIT-4 LCR BIT-3 X 0 0 1 1 X 0 1 0 1 0 1 1 1 1 PARITY SELECTION No parity Odd parity Even parity Force parity to mark, “1” Forced parity to space, “0” 30 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 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. 4.7 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 The DTR# pin is a modem control output. If the modem interface is not used, this output may be used as a general purpose output. • Logic 0 = Force DTR# output HIGH (default). • Logic 1 = Force DTR# output LOW. MCR[1]: RTS# Output The RTS# pin 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 bit3. 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 V2750. 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. • 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 12. 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 V2750 is programmed to use the Xon/Xoff flow control. MCR[6]: Infrared Encoder/Decoder Enable (requires EFR bit-4=1) • Logic 0 = Enable the standard modem receive and transmit input/output interface (default). • Logic 1 = Enable infrared IrDA receive and transmit inputs/outputs. The TX/RX output/input are routed to the infrared encoder/decoder. The data input and output levels conform to the IrDA infrared interface 31 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.3 requirement. While in this mode, the infrared TX output will be idling LOW. SEE”INFRARED MODE” ON PAGE 19. 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. 4.8 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. 32 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 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. MSR[0]: Delta CTS# Input Flag • 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 • 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 • 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 • 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# pin may function as automatic hardware flow control signal input if it is enabled and selected by Auto CTS (EFR bit-7). Auto CTS flow control allows starting and stopping of local data transmissions based on the modem CTS# signal. A HIGH on the CTS# pin will stop UART transmitter as soon as the current character has finished transmission, and a LOW will resume data transmission. Normally MSR bit-4 bit is the complement of the CTS# input. However in the loopback mode, this bit is equivalent to the RTS# bit in the MCR register. The CTS# input may be used as a general purpose input when the modem interface is not used. MSR[5]: DSR Input Status Normally this bit is the complement of the DSR# input. In the loopback mode, this bit is equivalent to the DTR# bit in the MCR register. The DSR# input may be used as a general purpose input when the modem interface is not used. 33 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO MSR[6]: RI Input Status Normally this bit is the complement of the RI# input. In the loopback mode this bit is equivalent to bit-2 in the MCR register. The RI# input may be used as a general purpose input when the modem interface is not used. MSR[7]: CD Input Status Normally this bit is the complement of the CD# input. In the loopback mode this bit is equivalent to bit-3 in the MCR register. The CD# input may be used as a general purpose input when the modem interface is not used. 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. 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 12: SCRATCHPAD SWAP SELECTION FCTR[6] EMSR[1] 0 1 1 1 X X 0 1 EMSR[0] Scratchpad is X 0 1 1 Scratchpad RX FIFO Level Counter Mode TX FIFO Level Counter Mode Alternate RX/TX FIFO Counter Mode REV. 1.0.3 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[2]: Reserved EMSR[3]: Automatic RS485 Half-Duplex Control Output Inversion • Logic 0 = RTS# output is LOW during TX and HIGH during RX (default, compatible with 16C2850). • Logic 1 = RTS# output is HIGH during TX and LOW during RX. EMSR[5:4]: Extended RTS Hysteresis TABLE 13: AUTO RTS HYSTERESIS EMSR BIT-5 0 0 0 0 0 0 0 0 EMSR BIT-4 0 0 0 0 1 1 1 1 FCTR BIT-1 0 0 1 1 0 0 1 1 FCTR BIT-0 0 1 0 1 0 1 0 1 RTS# HYSTERESIS (CHARACTERS) 0 ±4 ±6 ±8 ±8 ±16 ±24 ±32 34 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO TABLE 13: AUTO RTS HYSTERESIS EMSR BIT-5 1 1 1 1 1 1 1 1 EMSR BIT-4 0 0 0 0 1 1 1 1 FCTR BIT-1 0 0 1 1 0 0 1 1 FCTR BIT-0 0 1 0 1 0 1 0 1 RTS# HYSTERESIS (CHARACTERS) ±40 ±44 ±48 ±52 ±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. 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 12 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 11. 4.14 Device Identification Register (DVID) - Read Only This register contains the device ID (0x0A for XR16V2750). 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 programmable 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 35 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.3 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 12. 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 This register controls the XR16V2750 functions that are not available in ST16C2450 or ST16C2550. FCTR[1:0]: RTS Hysteresis User selectable RTS# hysteresis levels for hardware flow control application. After reset, these bits are set to “0” to select the next trigger level for hardware flow control. See Table 13 for more details. FCTR[2]: IrDa RX Inversion • Logic 0 = Select RX input as encoded IrDa data (Idle state will be LOW). • Logic 1 = Select RX input as inverted encoded IrDa data (Idle state will be HIGH). FCTR[3]: Auto RS-485 Direction Control • Logic 0 = Standard ST16C550 mode. Transmitter generates an interrupt when transmit holding register becomes empty and transmit shift register is shifting data out. • Logic 1 = Enable Auto RS485 Direction Control function. The direction control signal, RTS# pin, changes its output logic state from LOW to HIGH one bit time after the last stop bit of the last character is shifted out. Also, the Transmit interrupt generation is delayed until the transmitter shift register becomes empty. The RTS# output pin will automatically return to a LOW when a data byte is loaded into the TX FIFO. However, RTS# behavior can be inverted by setting EMSR[3] = 1. 36 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FCTR[5:4]: Transmit/Receive Trigger Table Select See Table 10 for more details. TABLE 14: TRIGGER TABLE SELECT FCTR BIT-5 0 0 1 1 FCTR BIT-4 0 1 0 1 TABLE Table-A (TX/RX) Table-B (TX/RX) Table-C (TX/RX) Table-D (TX/RX) 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 15). 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. 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. 37 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO TABLE 15: SOFTWARE FLOW CONTROL FUNCTIONS EFR BIT-3 CONT-3 0 0 1 0 1 X X X 1 EFR BIT-2 CONT-2 0 0 0 1 1 X X X 0 EFR BIT-1 CONT-1 0 X X X X 0 1 0 1 EFR BIT-0 CONT-0 0 X X X X 0 0 1 1 TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL No TX and RX flow control (default and reset) No transmit flow control Transmit Xon1, Xoff1 Transmit Xon2, Xoff2 Transmit Xon1 and Xon2, Xoff1 and Xoff2 No receive flow control Receiver compares Xon1, Xoff1 Receiver compares Xon2, Xoff2 Transmit Xon1, Xoff1 Receiver compares Xon1 or Xon2, Xoff1 or Xoff2 Transmit Xon2, Xoff2 Receiver compares Xon1 or Xon2, Xoff1 or Xoff2 Transmit Xon1 and Xon2, Xoff1 and Xoff2, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 No transmit flow control, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 REV. 1.0.3 0 1 1 1 1 1 1 1 0 0 1 1 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[5]: Special Character Detect Enable • Logic 0 = Special Character Detect Disabled (default). • Logic 1 = Special Character Detect Enabled. The UART compares each incoming receive character with data in Xoff-2 register. If a match exists, the receive data will be transferred to FIFO and ISR bit-4 will be set to indicate detection of the special character. Bit-0 corresponds with the LSB bit of the receive character. If flow control is set for comparing Xon1, Xoff1 (EFR [1:0]= ‘10’) then flow control and special character work normally. However, if flow control is set for comparing Xon2, Xoff2 (EFR[1:0]= ‘01’) then flow control works normally, but Xoff2 will not go to the FIFO, and will generate an Xoff interrupt and a special character interrupt, if enabled via IER bit-5. 38 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO EFR[6]: Auto RTS Flow Control Enable RTS# output may be used for hardware flow control by setting EFR bit-6 to logic 1. When Auto RTS is selected, an interrupt will be generated when the receive FIFO is filled to the programmed trigger level and RTS de-asserts HIGH at the next upper trigger level or hysteresis level. RTS# will return LOW when FIFO data falls below the next lower trigger level. The RTS# output must be asserted (LOW) before the auto RTS can take effect. RTS# pin will function as a general purpose output when hardware flow control is disabled. • Logic 0 = Automatic RTS flow control is disabled (default). • Logic 1 = Enable Automatic RTS flow control. EFR[7]: Auto CTS Flow Control Enable Automatic CTS Flow Control. • Logic 0 = Automatic CTS flow control is disabled (default). • Logic 1 = Enable Automatic CTS flow control. Data transmission stops when CTS# input de-asserts HIGH. Data transmission resumes when CTS# returns LOW. 4.19.1 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 6. 39 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO TABLE 16: UART RESET CONDITIONS FOR CHANNEL A AND B REGISTERS DLM, DLL DLD RHR THR IER FCR ISR LCR MCR LSR MSR RESET STATE DLM = 0x00 and DLL = 0x01. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. Bits 7-0 = 0x00 Bits 7-0 = 0xXX Bits 7-0 = 0xXX Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x01 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x60 Bits 3-0 = Logic 0 Bits 7-4 = Logic levels of the inputs inverted Bits 7-0 = 0xFF Bits 7-0 = 0x80 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 Bits 7-0 = 0x00 RESET STATE HIGH HIGH HIGH HIGH HIGH LOW Three-State Condition REV. 1.0.3 SPR EMSR FLVL EFR XON1 XON2 XOFF1 XOFF2 FC I/O SIGNALS TX OP2# RTS# DTR# RXRDY# TXRDY# INT 40 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO ABSOLUTE MAXIMUM RATINGS Power Supply Range Voltage at Any Pin Operating Temperature Storage Temperature Package Dissipation 4 Volts GND-0.3V to 5.5V -40o to +85oC -65o to +150oC 500 mW TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: ± 15%) Thermal Resistance (48-TQFP) Thermal Resistance (32-QFN) theta-ja =59oC/W, theta-jc = 16oC/W theta-ja = 33oC/W, theta-jc = 22oC/W ELECTRICAL CHARACTERISTICS DC ELECTRICAL CHARACTERISTICS TA=-40O TO +85OC, VCC IS 2.25V TO 3.6V SYMBOL PARAMETER LIMITS 2.5V MIN MAX -0.3 2.0 -0.3 1.8 0.4 VCC 0.5 5.5 LIMITS 3.3V MIN MAX -0.3 2.4 -0.3 2.0 0.6 VCC 0.7 5.5 0.4 0.4 VOH Output High Voltage 1.8 IIL IIH CIN ICC ISLEEP Input Low Leakage Current Input High Leakage Current Input Pin Capacitance Power Supply Current Sleep Current ±10 ±10 5 1.5 15 ±10 ±10 5 2.5 30 2.4 UNITS CONDITIONS VILCK VIHCK VIL VIH VOL Clock Input Low Level Clock Input High Level Input Low Voltage Input High Voltage Output Low Voltage V V V V V V V V uA uA pF mA uA Ext Clk = 2MHz See Test 1 IOL = 6 mA IOL = 4 mA IOH = -4 mA IOH = -2 mA Test 1: The following inputs must remain steady at VCC or GND state to minimize Sleep current: A0-A2, D0D7, IOR#, IOW#, CSA#, CSB# and all modem inputs. Also, RXA and RXB inputs must idle HIGH while asleep. Floating inputs will result in sleep currents in the mA range. For PowerSave feature that isolates address, data and control signals, please see the XR16V2751 datasheet. 41 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO AC ELECTRICAL CHARACTERISTICS UNLESS OTHERWISE NOTED: TA=-40O TO +85OC, VCC=2.25 - 3.63V, 70 PF LOAD WHERE APPLICABLE SYMBOL PARAMETER LIMITS 2.5V ± 10% MIN MAX 24 50 10 0 0 50 50 50 45 25 50 50 10 5 50 50 50 1 45 45 8 24 45 1 45 45 8 40 40 16X or 8X of data rate 8 40 40 10 5 50 50 50 1 45 45 24 45 1 45 45 8 7 0 0 40 40 40 35 25 LIMITS 3.3V ± 10% MIN MAX 24 64 UNIT REV. 1.0.3 XTAL1 ECLK TECLK TAS TAH TCS TRD TDY TRDV TDD TWR TDY TDS TDH TWDO TMOD TRSI TSSI TRRI TSI TINT TWRI TSSR TRR TWT TSRT TRST Bclk UART Crystal Oscillator External Clock External Clock Time Period Address Setup Time Address Hold Time Chip Select Width IOR# Strobe Width Read Cycle Delay Data Access Time Data Disable Time IOW# Strobe Width Write Cycle Delay Data Setup Time Data Hold Time Delay From IOW# To Output Delay To Set Interrupt From MODEM Input Delay To Reset Interrupt From IOR# Delay From Stop To Set Interrupt Delay From IOR# To Reset Interrupt Delay From Stop To Interrupt Delay From Initial INT Reset To Transmit Start Delay From IOW# To Reset Interrupt Delay From Stop To Set RXRDY# Delay From IOR# To Reset RXRDY# Delay From IOW# To Set TXRDY# Delay From Center of Start To Reset TXRDY# Reset Pulse Width Baud Clock MHz MHz ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns Bclk ns ns Bclk ns Bclk ns ns Bclk ns Hz 42 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 13. CLOCK TIMING TECLK TECH TECL VIH External Clock VIL FIGURE 14. MODEM INPUT/OUTPUT TIMING FOR CHANNELS A & B IOW # Active T W DO RTS# DTR# Change of state Change of state CD# CTS# DSR# T MO D INT Change of state Change of state T M OD Active T RSI Active Active IOR# Active Active Active T M OD RI# Change of state 43 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 15. DATA BUS READ TIMING REV. 1.0.3 A0-A2 TAS Valid Address TAS Valid Address TCS CSA#/ CSB# TAH TCS TAH TDY TRD IOR# TRD TRDV D0-D7 Valid Data TDD TRDV Valid Data TDD RDTm FIGURE 16. DATA BUS WRITE TIMING A0-A2 TAS Valid Address TAS Valid Address TCS CSA#/ CSB# TAH TCS TAH TDY TWR IOW# TWR TDS D0-D7 Valid Data TDH TDS Valid Data TDH 16Write 44 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 17. RECEIVE READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B RX Start Bit Stop Bit TSSR 1 Byte in RHR TSSR D0:D7 D0:D7 TSSR 1 Byte in RHR TSSR D0:D7 TSSR 1 Byte in RHR TSSR INT RXRDY# Active Data Ready TRR Active Data Ready TRR Active Data Ready TRR IOR# (Reading data out of RHR) RXNFM FIGURE 18. TRANSMIT READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B TX Start Bit IER[1] enabled Stop Bit D0:D7 D0:D7 D0:D7 ISR is read ISR is read ISR is read INT* TWRI TSRT TWRI TSRT TWRI TSRT TXRDY# TWT TWT TWT IOW# (Loading data into THR) *INT is cleared when the ISR is read or when data is loaded into the THR. TXNonFIFO 45 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.3 FIGURE 19. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA DISABLED] FOR CHANNELS A & B Start Bit RX S D0:D7 Stop Bit S D0:D7 T D0:D7 TSSI S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T RX FIFO drops below RX Trigger Level INT TSSR RXRDY# First Byte is Received in RX FIFO IOR# (Reading data out of RX FIFO) RX FIFO fills up to RX Trigger Level or RX Data Timeout FIFO Empties TRRI TRR RXINTDMA# FIGURE 20. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA ENABLED] FOR CHANNELS A & B Start Bit Stop Bit RX S D0:D7 S D0:D7 T D0:D7 TSSI S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T RX FIFO drops below RX Trigger Level INT RX FIFO fills up to RX Trigger Level or RX Data Timeout RXRDY# TSSR FIFO Empties TRRI TRR IOR# (Reading data out of RX FIFO) RXFIFODMA 46 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO FIGURE 21. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE DISABLED] FOR CHANNELS A & B Start Bit Stop Bit Last Data Byte Transmitted S D0:D7 T S D0:D7 T TSI T S D0:D7 T S D0:D7 T ISR is read TSRT S D0:D7 T TX FIFO Empty TX (Unloading) IER[1] enabled S D0:D7 T ISR is read INT* TX FIFO fills up to trigger level Data in TX FIFO TX FIFO Empty TWRI TX FIFO drops below trigger level TXRDY# TWT IOW# (Loading data into FIFO) *INT is cleared when the ISR is read or when TX FIFO fills up to the trigger level. TXDMA# FIGURE 22. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE ENABLED] FOR CHANNELS A & B Start Bit Stop Bit Last Data Byte Transmitted D0:D7 S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T ISR Read TX (Unloading) IER[1] enabled S D0:D7 T S D0:D7 T ISR Read TSRT TSI INT* TX FIFO fills up to trigger level TX FIFO drops below trigger level At least 1 empty location in FIFO TWRI TX FIFO Full TXRDY# TWT IOW# (Loading data into FIFO) *INT cleared when the ISR is read or when TX FIFO fills up to trigger level. TXDMA 47 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.3 PACKAGE DIMENSIONS (48 PIN TQFP - 7 X 7 X 1 mm) D D1 36 25 37 24 D1 D 48 13 1 B A2 e 1 2 C A Seating Plane A1 L α Note: The control dimension is the millimeter column INCHES SYMBOL A A1 A2 B C D D1 e L a MIN 0.039 0.002 0.037 0.007 0.004 0.346 0.272 MAX 0.047 0.006 0.041 0.011 0.008 0.362 0.280 MILLIMETERS MIN 1.00 0.05 0.95 0.17 0.09 8.80 6.90 MAX 1.20 0.15 1.05 0.27 0.20 9.20 7.10 0.020 BSC 0.018 0° 0.030 7° 0.50 BSC 0.45 0° 0.75 7° 48 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO PACKAGE DIMENSIONS (32 PIN QFN - 5 X 5 X 0.9 mm) Note: the actual center pad is metallic and the size (D2) is device-dependent with a typical tolerance of 0.3mm Note: The control dimension is in millimeter. INCHES SYMBOL A A1 A3 D D2 b e L k MIN 0.031 0.000 0.006 0.193 0.138 0.007 MAX 0.039 0.002 0.010 0.201 0.150 0.012 MILLIMETERS MIN 0.80 0.00 0.15 4.90 3.50 0.18 MAX 1.00 0.05 0.25 5.10 3.80 0.30 0.0197 BSC 0.012 0.008 0.020 - 0.50 BSC 0.35 0.20 0.45 - 49 XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REVISION HISTORY DATE June 2006 January 2007 May 2007 May 2007 September 2007 REVISION P1.0.0 1.0.0 1.0.1 1.0.2 1.0.3 Preliminary Datasheet. Final Datasheet. Updated AC Electrical Characteristics. Added "GND Center Pad" to pin description. Updated 32 pin QFN package dimensions drawing to show minimum "k" parameter. Updated Pin description table. Corrected maximum crystal frequency to 24 MHz at 2.5 V power supply. DESCRIPTION REV. 1.0.3 NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user’s specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation 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 EXAR Corporation is adequately protected under the circumstances. Copyright 2007 EXAR Corporation Datasheet September 2007. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. 50 XR16V2750 REV. 1.0.3 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO TABLE OF CONTENTS GENERAL DESCRIPTION................................................................................................ 1 APPLICATIONS .............................................................................................................................................. 1 FEATURES .................................................................................................................................................... 1 FIGURE 1. XR16V2750 BLOCK DIAGRAM ......................................................................................................................................... 1 FIGURE 2. PIN OUT ASSIGNMENT ..................................................................................................................................................... 2 ORDERING INFORMATION ............................................................................................................................... 2 PIN DESCRIPTIONS ........................................................................................................ 3 1.0 PRODUCT DESCRIPTION ...................................................................................................................... 7 2.0 FUNCTIONAL DESCRIPTIONS .............................................................................................................. 8 2.1 CPU INTERFACE ................................................................................................................................................ 8 FIGURE 3. XR16V2750 DATA BUS INTERCONNECTIONS ................................................................................................................... 8 2.2 5-VOLT TOLERANT INPUTS .............................................................................................................................. 2.3 DEVICE RESET ................................................................................................................................................... 2.4 DEVICE IDENTIFICATION AND REVISION ....................................................................................................... 2.5 CHANNEL A AND B SELECTION ...................................................................................................................... 8 8 8 8 TABLE 1: CHANNEL A AND B SELECT ............................................................................................................................................... 9 2.6 CHANNEL A AND B INTERNAL REGISTERS ................................................................................................... 9 2.7 DMA MODE ......................................................................................................................................................... 9 TABLE 2: TXRDY# AND RXRDY# OUTPUTS IN FIFO AND DMA MODE ............................................................................................. 9 2.8 INTA AND INTB OUTPUTS............................................................................................................................... 10 TABLE 3: INTA AND INTB PINS OPERATION FOR TRANSMITTER ...................................................................................................... 10 TABLE 4: INTA AND INTB PIN OPERATION FOR RECEIVER ............................................................................................................. 10 2.9 CRYSTAL OSCILLATOR OR EXTERNAL CLOCK INPUT.............................................................................. 10 FIGURE 4. TYPICAL OSCILLATOR CONNECTIONS............................................................................................................................... 10 2.10 PROGRAMMABLE BAUD RATE GENERATOR WITH FRACTIONAL DIVISOR ......................................... 11 FIGURE 5. BAUD RATE GENERATOR ............................................................................................................................................... 12 TABLE 5: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING ................................................... 12 2.11 TRANSMITTER................................................................................................................................................ 13 2.11.1 TRANSMIT HOLDING REGISTER (THR) - WRITE ONLY......................................................................................... 2.11.2 TRANSMITTER OPERATION IN NON-FIFO MODE .................................................................................................. FIGURE 6. TRANSMITTER OPERATION IN NON-FIFO MODE .............................................................................................................. 2.11.3 TRANSMITTER OPERATION IN FIFO MODE ........................................................................................................... FIGURE 7. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE ..................................................................................... 13 13 13 13 14 2.12 RECEIVER ....................................................................................................................................................... 14 2.12.1 RECEIVE HOLDING REGISTER (RHR) - READ-ONLY ............................................................................................ 14 FIGURE 8. RECEIVER OPERATION IN NON-FIFO MODE .................................................................................................................... 15 FIGURE 9. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE ......................................................................... 15 2.13 AUTO RTS (HARDWARE) FLOW CONTROL ................................................................................................ 16 2.14 AUTO RTS HYSTERESIS .............................................................................................................................. 16 2.15 AUTO CTS FLOW CONTROL........................................................................................................................ 16 FIGURE 10. AUTO RTS AND CTS FLOW CONTROL OPERATION ....................................................................................................... 17 2.16 AUTO XON/XOFF (SOFTWARE) FLOW CONTROL...................................................................................... 18 TABLE 6: AUTO XON/XOFF (SOFTWARE) FLOW CONTROL ............................................................................................................... 18 2.17 SPECIAL CHARACTER DETECT.................................................................................................................. 18 2.18 AUTO RS485 HALF-DUPLEX CONTROL ..................................................................................................... 18 2.19 INFRARED MODE ........................................................................................................................................... 19 FIGURE 11. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING .......................................................................... 19 2.20 SLEEP MODE WITH AUTO WAKE-UP ......................................................................................................... 20 2.21 INTERNAL LOOPBACK................................................................................................................................. 21 FIGURE 12. INTERNAL LOOP BACK IN CHANNEL A AND B ................................................................................................................ 21 3.0 UART INTERNAL REGISTERS............................................................................................................. 22 TABLE 7: UART CHANNEL A AND B UART INTERNAL REGISTERS ...................................................................................... 22 TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1 ......................................... 23 4.0 INTERNAL REGISTER DESCRIPTIONS .............................................................................................. 24 4.1 RECEIVE HOLDING REGISTER (RHR) - READ- ONLY .................................................................................. 24 4.2 TRANSMIT HOLDING REGISTER (THR) - WRITE-ONLY ............................................................................... 24 4.3 INTERRUPT ENABLE REGISTER (IER) - READ/WRITE ................................................................................ 24 4.3.1 IER VERSUS RECEIVE FIFO INTERRUPT MODE OPERATION ............................................................................... 25 4.3.2 IER VERSUS RECEIVE/TRANSMIT FIFO POLLED MODE OPERATION.................................................................. 25 I XR16V2750 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.3 4.4 INTERRUPT STATUS REGISTER (ISR) - READ-ONLY .................................................................................. 26 4.4.1 INTERRUPT GENERATION: ........................................................................................................................................ 26 4.4.2 INTERRUPT CLEARING: ............................................................................................................................................. 26 TABLE 9: INTERRUPT SOURCE AND PRIORITY LEVEL ....................................................................................................................... 27 4.5 FIFO CONTROL REGISTER (FCR) - WRITE-ONLY......................................................................................... 27 TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER TABLE AND LEVEL SELECTION .......................................................................... 29 4.6 LINE CONTROL REGISTER (LCR) - READ/WRITE......................................................................................... 29 TABLE 11: PARITY SELECTION ........................................................................................................................................................ 30 4.7 MODEM CONTROL REGISTER (MCR) OR GENERAL PURPOSE OUTPUTS CONTROL - READ/WRITE.. 4.8 LINE STATUS REGISTER (LSR) - READ ONLY.............................................................................................. 4.9 MODEM STATUS REGISTER (MSR) - READ ONLY ....................................................................................... 4.10 SCRATCH PAD REGISTER (SPR) - READ/WRITE ....................................................................................... 4.11 ENHANCED MODE SELECT REGISTER (EMSR) ......................................................................................... 31 32 33 34 34 TABLE 12: SCRATCHPAD SWAP SELECTION .................................................................................................................................... 34 TABLE 13: AUTO RTS HYSTERESIS ................................................................................................................................................ 34 4.12 FIFO LEVEL REGISTER (FLVL) - READ-ONLY............................................................................................. 4.13 BAUD RATE GENERATOR REGISTERS (DLL, DLM AND DLD) - READ/WRITE ....................................... 4.14 DEVICE IDENTIFICATION REGISTER (DVID) - READ ONLY....................................................................... 4.15 DEVICE REVISION REGISTER (DREV) - READ ONLY ................................................................................. 4.16 TRIGGER LEVEL REGISTER (TRG) - WRITE-ONLY .................................................................................... 4.17 RX/TX FIFO LEVEL COUNT REGISTER (FC) - READ-ONLY ....................................................................... 4.18 FEATURE CONTROL REGISTER (FCTR) - READ/WRITE........................................................................... 35 35 35 35 35 35 36 TABLE 14: TRIGGER TABLE SELECT ................................................................................................................................................ 37 4.19 ENHANCED FEATURE REGISTER (EFR) ..................................................................................................... 37 TABLE 15: SOFTWARE FLOW CONTROL FUNCTIONS ........................................................................................................................ 38 4.19.1 SOFTWARE FLOW CONTROL REGISTERS (XOFF1, XOFF2, XON1, XON2) - READ/WRITE .............................. 39 TABLE 16: UART RESET CONDITIONS FOR CHANNEL A AND B ............................................................................................ 40 ABSOLUTE MAXIMUM RATINGS.................................................................................. 41 TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: ± 15%) 41 ELECTRICAL CHARACTERISTICS ............................................................................... 41 DC ELECTRICAL CHARACTERISTICS ............................................................................................................. 41 TA=-40o to +85oC, Vcc is 2.25V to 3.6V................................................................................................................ 41 AC ELECTRICAL CHARACTERISTICS ............................................................................................................. 42 Unless otherwise noted: TA=-40o to +85oC, Vcc=2.25 - 3.63V, 70 pF load where applicable ................................ 42 FIGURE 13. CLOCK TIMING ............................................................................................................................................................. FIGURE 14. MODEM INPUT/OUTPUT TIMING FOR CHANNELS A & B ................................................................................................. FIGURE 16. DATA BUS WRITE TIMING............................................................................................................................................. FIGURE 15. DATA BUS READ TIMING .............................................................................................................................................. FIGURE 17. RECEIVE READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B ......................................................... FIGURE 18. TRANSMIT READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B ....................................................... FIGURE 19. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA DISABLED] FOR CHANNELS A & B ........................................ FIGURE 20. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA ENABLED] FOR CHANNELS A & B ......................................... FIGURE 21. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE DISABLED] FOR CHANNELS A & B............................ FIGURE 22. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE ENABLED] FOR CHANNELS A & B ............................ 43 43 44 44 45 45 46 46 47 47 PACKAGE DIMENSIONS (48 PIN TQFP - 7 X 7 X 1 mm) ............................................... 48 PACKAGE DIMENSIONS (32 PIN QFN - 5 X 5 X 0.9 mm) .............................................. 49 REVISION HISTORY...................................................................................................................................... 50 II