XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO MAY 2007 REV. 1.0.2 GENERAL DESCRIPTION The XR16M752/XR68M7521 (M752) is a high performance dual universal asynchronous receiver and transmitter (UART) with 64 byte TX and RX FIFOs. The M752 operates from 1.62 to 3.63 volts. It is pin-to-pin and software compatible to the TL16C752B and SC16C752B, but with additional features such as a programmable fractional baud rate generator, automatic RS-485 half-duplex direction control, infrared mode and 8X and 4X sampling rate. The standard features include 16 selectable TX and RX FIFO trigger levels, automatic hardware (RTS/ CTS) and software (Xon/Xoff) flow control, and a complete modem interface. Onboard registers provide the user with operational status and data error flags. An internal loopback capability allows system diagnostics. Each channel is independently programmable for data rates up to 16 Mbps at 3.3 Volt with a 4X sampling rate. The XR68M752 has an additional 16/68# pin to select between the Intel and Motorola bus interface. The M752 is available in the 48-pin TQFP and 32-pin QFN packages. FEATURES • 1.62 to 3.6 Volt Operation • Pin-to-pin and software compatible to TI’s TL16C752B and Philips’ SC16C752B in the 48TQFP package • Two independent UART channels NOTE: 1 Covered by U.S. Patent #5,649,122 APPLICATIONS • Portable Appliances • Telecommunication Network Routers • Ethernet Network Routers • Cellular Data Devices • Factory Automation and Process Controls ■ Data rate of up to 16 Mbps at 3.3 V ■ Data rate of up to 12.5 Mbps at 2.5 V ■ Data rate of up to 8 Mbps at 1.8 V ■ Fractional Baud Rate Generator ■ Data sampling rates of 16X, 8X and 4X ■ Transmit and Receive FIFOs of 64 bytes ■ Programmable TX and RX FIFO Trigger Levels ■ Automatic Hardware (RTS/CTS) Flow Control ■ Automatic Software (Xon/Xoff) Flow Control ■ Halt and Resume Transmission Control ■ Automatic RS-485 Half-duplex Control Output via RTS# ■ Wireless Infrared (IrDA 1.0) Encoder/Decoder ■ Automatic sleep mode ■ Full modem interface Direction • Crystal oscillator (up to 24MHz) or external clock (up to 64MHz) input • 48-TQFP and 32-QFN packages FIGURE 1. XR16M752 BLOCK DIAGRAM 1.62 to 3.63 Volt VCC A2:A0 D7:D0 GND IOR# (NC) IOW# (R/W#) UART Channel A CSA# (CS#) CSB# (A3) INTA (IRQ#) INTB (NC) TXRDYA# TXRDYB# RXRDYA# RXRDYB# Reset/Reset# 16/68# UART Regs 8-bit Data Bus Interface BRG 64 Byte TX FIFO TX & RX IR ENDEC TXA, RXA, DTRA#, DSRA#, RTSA#, DTSA#, CDA#, RIA#, OP2A# 64 Byte RX FIFO UART Channel B (same as Channel A) Crystal Osc/Buffer TXB, RXB, DTRB#, DSRB#, RTSB#, CTSB#, CDB#, RIB#, OP2B# XTAL1 XTAL2 Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 RTSA# RXA 5 32 OP2A# TXRDYB# 6 31 RXRDYA# TXA 7 30 INTA TXB 8 29 INTB OP2B# 9 28 A0 CSA# 10 27 A1 CSB# 11 26 A2 NC 12 25 NC D5 1 36 RESET D6 2 35 DTRB# D7 3 34 DTRA# RXB 4 33 RTSA# RXA 5 32 OP2A# TXRDYB# 6 31 RXRDYA # 29 D2 31 D4 TXA 5 21 INTB 20 A0 GND 13 RTSB# 15 CTSB# 16 D0 VCC CTSA# 27 26 25 IOR# 14 IOW# 12 D1 NC 29 D2 17 28 8 XTAL2 11 A2 CSB# 30 D3 A1 18 NC 19 7 XTAL1 10 6 31 D4 TXB CSA# RESET D6 1 24 D7 2 23 RTSA# 22 INTA RXB 3 RXA 4 TXA 5 XR68M752 32-pin QFN Intel Mode 21 INTB 20 A0 A1 16/68# IOR# 14 CTSB# 16 17 CTSA# 8 25 A2 CSB# RTSB# 15 18 VCC 19 7 26 6 D0 TXB CSA# 27 24 16/68# INTA XR16M752 32-pin QFN Intel Mode Only GND 13 23 CTSB# 22 4 IOW# 12 22 RTSB# 3 RXA D1 21 DSRA# CTSA# NC 38 37 D5 1 36 RESET# D6 2 35 DTRB# D7 3 34 DTRA# D6 1 24 RXB 4 33 RTSA# D7 2 23 RTSA# RXA 5 32 OP2A# RXB 3 22 IRQ# RXA 4 TXRDYB# 6 31 RXRDYA # TXA 5 TXA 7 IRQ# TXB TXB 8 CS# A3 18 19 20 21 22 23 24 RXRDYB# NC DSRB# RIB# RTSB# CTSB# 16/68# 16/68# GND 2 NC CTSB# 16 17 RTSB# 15 A2 8 14 A1 18 12 19 7 GND 13 6 R/W# NC 17 A2 25 GND 26 12 15 11 16 A3 NC CDB# A1 14 A0 27 R/W# 28 10 XTAL2 9 CS# 13 OP2B# A0 XTAL2 11 NC NC 20 9 29 RESET# 21 NC 30 XR68M752 32-pin QFN Motorola Mode XTAL1 10 XR68M752 48- pin TQFP Motorola Mode XTAL1 VCC VCC 39 CDA# 40 RIB# RIA# 41 20 VCC 42 DSRB# TXRDYA# 43 19 D0 44 18 D1 45 IOR# D2 46 RXRDYB# D3 47 16 NC 17 A2 25 GND 26 12 CDB# 11 NC 15 CSB # IOW# 27 13 10 14 RXB 29 D2 A1 CSA # XTAL2 RTSA# 28 INTB A0 30 D3 32 D5 29 9 XTAL1 RESET 23 9 INTA OP2B# D4 24 2 32 D5 NC NC 37 23 24 CTSB# DSRA# CDA# 40 CTSA# RIA# 41 38 22 VCC 42 RTSB# 21 TXRDYA# 43 RIB# 19 20 RXRDYB# IOR# 18 GND D0 DSRB# 16 17 CDB# D1 45 44 15 IOW# D2 46 13 14 XTAL2 D3 XTAL1 D4 48 47 39 30 28 48 1 D7 XTAL2 11 8 D6 30 D3 TXB DTRB# 9 7 XR68M 752 48- pin TQFP Intel Mode RESET NC TXA XR16M752 48-pin TQFP Intel Mode Only VCC 33 CTSA# 4 25 DTRA# RXB D0 34 26 3 D1 D7 27 35 28 36 2 XTAL1 10 37 1 D6 31 D4 CTSA# NC 38 D5 32 D5 CDA# DSRA# RIA# 41 39 VCC 42 40 D0 TXRDYA# 43 D1 45 44 D3 D2 46 D4 48 47 FIGURE 2. PIN OUT ASSIGNMENT GND XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 ORDERING INFORMATION PART NUMBER PACKAGE OPERATING TEMPERATURE RANGE DEVICE STATUS XR16M752IL32 32-pin QFN -40°C to +85°C Active XR16M752IM48 48-Lead TQFP -40°C to +85°C Active XR68M752IL32 32-pin QFN -40°C to +85°C Active XR68M752IM48 48-Lead TQFP -40°C to +85°C Active PIN DESCRIPTIONS Pin Description NAME 32-QFN PIN # 48-TQFP PIN # TYPE DESCRIPTION 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 INTERFACE A2 A1 A0 18 19 20 26 27 28 I D7 D6 D5 D4 D3 D2 D1 D0 2 1 32 31 30 29 28 27 3 2 1 48 47 46 45 44 I/O IOR# (NC) 14 19 I When 16/68# pin is HIGH, the Intel bus interface is selected and this input becomes read strobe (active low). The falling edge instigates an internal read cycle and retrieves the data byte from an internal register pointed by the address lines [A2:A0], puts the data byte on the data bus to allow the host processor to read it on the rising edge. When 16/68# pin is LOW, the Motorola bus interface is selected and this input is not used. IOW# (R/W#) 12 15 I When 16/68# pin is HIGH, it selects Intel bus interface and this input becomes write strobe (active low). The falling edge instigates the internal write cycle and the rising edge transfers the data byte on the data bus to an internal register pointed by the address lines. When 16/68# pin is LOW, the Motorola bus interface is selected and this input becomes read (HIGH) and write (LOW) signal. CSA# (CS#) 7 10 I When 16/68# pin is HIGH, this input is chip select A (active low) to enable channel A in the device. When 16/68# pin is LOW, this input becomes the chip select (active low) for the Motorola bus interface. CSB# (A3) 8 11 I When 16/68# pin is HIGH, this input is chip select B (active low) to enable channel B in the device. When 16/68# pin is LOW, this input becomes address line A3 which is used for channel selection in the Motorola bus interface. Input logic 0 selects channel A and logic 1 selects channel B. Data bus lines [7:0] (bidirectional). 3 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 Pin Description 32-QFN PIN # 48-TQFP PIN # TYPE DESCRIPTION INTA (IRQ#) 22 30 O When 16/68# pin is HIGH for Intel bus interface, this output becomes 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# to HIGH when MCR[3] is set to a logic 0. See MCR[3]. When 16/68# pin is LOW for Motorola bus interface, this output becomes device interrupt output (active low, open drain). An external pull-up resistor is required for proper operation. INTB (NC) 21 29 O When 16/68# pin is HIGH for Intel bus interface, this output becomes 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 OP2A# output to LOW when MCR[3] is set to a logic 1. INTA is set to the three state mode and OP2A# to HIGH when MCR[3] is set to a logic 0. See MCR[3]. When 16/68# pin is LOW for Motorola bus interface, this output is not used. TXRDYA# - 43 O UART channel A Transmitter Ready (active low). The output provides the TX FIFO/THR status for transmit channel A. See Table 3. If it is not used, leave it unconnected. RXRDYA# - 31 O UART channel A Receiver Ready (active low). This output provides the RX FIFO/RHR status for receive channel A. See Table 3. If it is not used, leave it unconnected. TXRDYB# - 6 O UART channel B Transmitter Ready (active low). The output provides the TX FIFO/THR status for transmit channel B. See Table 4. If it is not used, leave it unconnected. RXRDYB# - 18 O UART channel B Receiver Ready (active low). This output provides the RX FIFO/RHR status for receive channel B. See Table 3. If it is not used, leave it unconnected. NAME 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. RXA 4 5 I 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]. If this pin is not used, tie it to VCC or pull it high via a 100k ohm resistor. RTSA# 23 33 O 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] and IER[6]. For auto RS485 half-duplex direction control, see DLD[6]. 4 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 Pin Description NAME 32-QFN PIN # 48-TQFP PIN # TYPE CTSA# 25 38 I 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 or GND when not used. DTRA# - 34 O UART channel A Data-Terminal-Ready (active low) or general purpose output. If it is not used, leave it unconnected. DSRA# - 39 I UART channel A Data-Set-Ready (active low) or general purpose input. This input should be connected to VCC or GND when not used. CDA# - 40 I UART channel A Carrier-Detect (active low) or general purpose input. This input should be connected to VCC or GND when not used. RIA# - 41 I UART channel A Ring-Indicator (active low) or general purpose input. This input should be connected to VCC or GND when not used. OP2A# - 32 O 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. TXB 6 8 O 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. RXB 3 4 I 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]. If this pin is not used, tie it to VCC or pull it high via a 100k ohm resistor. RTSB# 15 22 O 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] and IER[6]. For auto RS485 half-duplex direction control, see DLD[6]. CTSB# 16 23 I 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 or GND when not used. DTRB# - 35 O UART channel B Data-Terminal-Ready (active low) or general purpose output. If it is not used, leave it unconnected. DSRB# - 20 I UART channel B Data-Set-Ready (active low) or general purpose input. This input should be connected to VCC or GND when not used. CDB# - 16 I UART channel B Carrier-Detect (active low) or general purpose input. This input should be connected to VCC or GND when not used. RIB# - 21 I UART channel B Ring-Indicator (active low) or general purpose input. This input should be connected to VCC or GND when not used. DESCRIPTION 5 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 Pin Description NAME 32-QFN PIN # 48-TQFP PIN # TYPE DESCRIPTION OP2B# - 9 O 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. ANCILLARY SIGNALS XTAL1 10 13 I Crystal or external clock input. XTAL2 11 14 O Crystal or buffered clock output. 16/68# 17 24 I Intel or Motorola Bus Select (internal pull-up resistor). This pin is not available for the XR16M752. This pin is available for the XR68M752 only. When 16/68# pin is HIGH, 16 or Intel Mode, the device will operate in the Intel bus type of interface. When 16/68# pin is LOW, 68 or Motorola mode, the device will operate in the Motorola bus type of interface. RESET (RESET#) 24 36 I When 16/68# pin is HIGH for Intel bus interface, this input becomes RESET (active high). When 16/68# pin is LOW for Motorola bus interface, this input becomes RESET# (active low). A 40 ns minimum active pulse on this pin will reset the internal registers and all outputs of channel A and B. The UART transmitter output will be held HIGH, the receiver input will be ignored and outputs are reset during reset period (see Table 16). VCC 26 42 Pwr 1.62V to 3.63V power supply. GND 13 17 Pwr Power supply common, ground. GND Center Pad - Pwr The center pad on the backside of the 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. NC 9 12, 25, 37 No Connection. Pin type: I=Input, O=Output, I/O= Input/output, OD=Output Open Drain. 6 XR16M752/XR68M752 REV. 1.0.2 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 1.0 PRODUCT DESCRIPTION The XR16M752/XR68M752 (M752) 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, automatic Xon/Xoff and special character software flow control, programmable transmit and receive FIFO trigger levels, 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 16 Mbps with 4X sampling clock rate. The XR16M752 is a 1.62V to 3.63V device. The M752 is fabricated with an advanced CMOS process. Enhanced Features The M752 DUART provides a solution that supports 64 bytes of transmit and receive FIFO memory, instead of 16 bytes in the industry standard 16C550. The M752 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 M752 by the larger transmit and receive FIFOs, FIFO trigger level control and automatic flow control mechanism. This allows the external processor to handle more networking tasks within a given time. For example, the 16C550 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 M752, 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 M752 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 DLD Bit-6 to “1”. This pin is HIGH for receive state and LOW for transmit state. Data Rate The M752 is capable of operation up to 16 Mbps at 3.3V with 4X internal sampling clock rate, 8 Mbps at 3.3V with 8X sampling clock rate, and 4 Mbps at 3.3V with 16X internal sampling clock rate. The device can operate with an external 24 MHz crystal 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 3.68 Mbps. The rich feature set of the M752 is available through the internal registers. Automatic hardware/software flow control, programmable transmit and receive FIFO trigger levels, programmable 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 M752 is software compatible with previous generation of UARTs, 16C450, 16C550 and 16C2550. 7 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 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 XR16M752 data interface supports the Intel compatible types of CPUs while the XR68M752 supports both the Intel and Motorola compatible data interfaces. 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. XR16M752/XR68M752 DATA BUS INTERCONNECTIONS VCC D0 D1 D2 D3 D4 D5 D6 D7 D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A0 A1 DSRA# A2 RIA# OP2A# IO R# IOR # IO W # IOW # RXA UART Channel A UART_INTA INTA UART_INTB INTB TXRDYA# RXRDYA# TXRDYB# TXRDYB# RXRDYB# RXRDYB# UART_RESET CTSA# Serial Interface of RS-232, RS-422 or RS-485 (no connect) TXB RXB UART Channel B TXRDYA# RXRDYA# DTRA# RTSA# CDA# CSA# CSB# UART_CSA# UART_CSB# VCC TXA DTRB# RTSB# CTSB# DSRB# CDB# RIB# OP2B# RESET Serial Interface of RS-232, RS-422 or RS-485 (no connect) GND Intel Data Bus Interconnections D0 D1 D2 D3 D4 D5 D6 D7 D0 D1 D2 D3 D4 D5 D6 D7 A0 A1 A2 A0 A1 A3 CSB# VCC RXA UART Channel A DTRA# RTSA# CTSA# DSRA# A2 Serial Interface of RS-232, RS-422 or RS-485 CDA# RIA# OP2A# IOR # VCC 2.25 to 3.6 Volt VCC TXA (no connect) IOW # R/W # TXB UART_CS# CSA# VCC UART_IRQ# INTA (no connect) RXB UART Channel B INTB DTRB# RTSB# CTSB# DSRB# TXRDYA# CDB# RXRDYA# RXRDYA# TXRDYB# TXRDYB# RIB# OP2B# RXRDYB# RXRDYB# TXRDYA# UART_RESET# RESET # M otorola Data Bus Interconnections 8 G ND Serial Interface of RS-232, RS-422 or RS-485 (no connect) XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 2.2 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. 2.3 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. During Intel Bus Mode (16/68# pin connected to VCC), a logic 0 on 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 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 IN 16 MODE CSA# CSB# FUNCTION 1 1 UART de-selected 0 1 Channel A selected 1 0 Channel B selected 0 0 Channel A and B selected During Motorola Bus Mode (16/68# pin connected to GND), the package interface pins are configured for connection with Motorola, and other popular microprocessor bus types. In this mode the M752 decodes an additional address, A3, to select one of the UART ports. The A3 address decode function is used only when in the Motorola Bus Mode. See Table 2. TABLE 2: CHANNEL A AND B SELECT IN 68 MODE 2.4 CS# A3 FUNCTION 1 N/A UART de-selected 0 0 Channel A selected 0 1 Channel B selected Channel A and B Internal Registers Each UART channel in the M752 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 16C550 features and capabilities, the M752 offers enhanced feature registers (EFR, Xon/ Xoff 1, Xon/Xoff 2, TCR, TLR and DLD) that provide automatic RTS and CTS hardware flow control, Xon/Xoff software flow control, automatic RS-485 half-duplex direction output enable/disable, and programmable FIFO trigger level control. All the register functions are discussed in full detail later in “Section 3.0, UART Internal Registers” on page 22. 9 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.5 REV. 1.0.2 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 M752 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 M752 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 19 through 24. TABLE 3: 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. TXRDY# A/B LOW = THR empty. LOW = FIFO empty. HIGH = byte in THR. HIGH = at least 1 byte in FIFO. 2.6 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 or LSR[7] = 1. LOW = FIFO is below the trigger level. HIGH = FIFO is full. INTA and INTB Outputs The INTA and INTB interrupt output changes according to the operating mode and enhanced features setup. Table 4 and 5 summarize the operating behavior for the transmitter and receiver. Also see Figures 19 through 24. TABLE 4: INTA AND INTB PINS OPERATION FOR TRANSMITTER Auto RS485 Mode FCR BIT-0 = 0 (FIFO DISABLED) FCR BIT-0 = 1 (FIFO ENABLED) INTA/B Pin NO LOW = a byte in THR HIGH = THR empty LOW = FIFO above trigger level HIGH = FIFO below trigger level or FIFO empty INTA/B Pin YES LOW = a byte in THR HIGH = transmitter empty LOW = FIFO above trigger level HIGH = FIFO below trigger level or transmitter empty TABLE 5: 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 10 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 2.7 Crystal Oscillator or External Clock Input The M752 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 2.8, Programmable Baud Rate Generator with Fractional Divisor” on page 11.” FIGURE 4. TYPICAL OSCILLATOR CONNECTIONS XTAL1 XTAL2 R2 500 ΚΩ − 1 ΜΩ Y1 C1 22-47 pF R1 0-120 Ω (Optional) 1.8432 MHz to 24 MHz C2 22-47 pF 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. However, with an external clock input on XTAL1 pin, it can extend its operation up to 64 MHz (16 Mbps serial data rate) at 3.3V with an 4X 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. 2.8 Programmable Baud Rate Generator with Fractional Divisor Each UART has its own Baud Rate Generator (BRG) with a prescaler for the transmitter and receiver. The prescaler is controlled by a software bit in the MCR register. The MCR register bit-7 sets the prescaler to divide the input crystal or external clock by 1 or 4. The output of the prescaler clocks to the BRG. The BRG further divides this clock by a programmable divisor between 1 and (216 - 0.0625) in increments of 0.0625 (1/16) to obtain a 16X, 8X or 4X 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. The four lower bits of the DLD 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 6 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 6. At 8X sampling rate, these data rates would double and at 4X sampling rate, these data rates would quadruple. Also, when using 8X sampling mode, the bit time will have a jitter of ± 1/16 whenever the DLD is non-zero and is an odd number. 11 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 When using 4X sampling mode, the bit time will have a jitter of ± 1/8 whenever DLD is non-zero, odd and not a multiple of 4. When using a non-standard 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, DLD[5:4]=’00’ Required Divisor (decimal)= (XTAL1 clock frequency / prescaler / (serial data rate x 8), with 8X mode, DLD[5:4] = ’01’ Required Divisor (decimal)= (XTAL1 clock frequency / prescaler / (serial data rate x 4), with 4X mode, DLD[5:4] = ’10’ The closest divisor that is obtainable in the M752 can be calculated using the following formula: ROUND( (Required Divisor - TRUNC(Required Divisor) )*16)/16 + TRUNC(Required Divisor), where DLM = TRUNC(Required Divisor) >> 8 DLL = TRUNC(Required Divisor) & 0xFF DLD = ROUND( (Required Divisor-TRUNC(Required Divisor) )*16) In the formulas above, please note that: TRUNC (N) = Integer Part of N. For example, TRUNC (5.6) = 5. ROUND (N) = N rounded towards the closest integer. For example, ROUND (7.3) = 7 and ROUND (9.9) = 10. A >> B indicates right shifting the value ’A’ by ’B’ number of bits. For example, 0x78A3 >> 8 = 0x0078. FIGURE 5. BAUD RATE GENERATOR To Other Channel DLL, DLM and DLD Registers Prescaler Divide by 1 XTAL1 XTAL2 Crystal Osc/ Buffer Prescaler Divide by 4 12 MCR Bit-7=0 (default) Fractional Baud Rate Generator Logic MCR Bit-7=1 16X or 8X or 4X Sampling Rate Clock to Transmitter and Receiver XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 TABLE 6: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING Required Output Data Rate DIVISOR FOR 16x Clock (Decimal) DIVISOR OBTAINABLE IN M752 DLM PROGRAM VALUE (HEX) DLL PROGRAM VALUE (HEX) DLD PROGRAM VALUE (HEX) DATA ERROR RATE (%) 400 3750 3750 E A6 0 0 2400 625 625 2 71 0 0 4800 312.5 312 8/16 1 38 8 0 9600 156.25 156 4/16 0 9C 4 0 10000 150 150 0 96 0 0 19200 78.125 78 2/16 0 4E 2 0 25000 60 60 0 3C 0 0 28800 52.0833 52 1/16 0 34 1 0.04 38400 39.0625 39 1/16 0 27 1 0 50000 30 30 0 1E 0 0 57600 26.0417 26 1/16 0 1A 1 0.08 75000 20 20 0 14 0 0 100000 15 15 0 F 0 0 115200 13.0208 13 0 D 0 0.16 153600 9.7656 9 12/16 0 9 C 0.16 200000 7.5 7 8/16 0 7 8 0 225000 6.6667 6 11/16 0 6 B 0.31 230400 6.5104 6 8/16 0 6 8 0.16 250000 6 6 0 6 0 0 300000 5 5 0 5 0 0 400000 3.75 3 12/16 0 3 C 0 460800 3.2552 3 4/16 0 3 4 0.16 500000 3 3 0 3 0 0 750000 2 2 0 2 0 0 921600 1.6276 1 10/16 0 1 A 0.16 1000000 1.5 1 8/16 0 1 8 0 2.9 Transmitter The transmitter section comprises of an 8-bit Transmit Shift Register (TSR) and 64 bytes of FIFO which includes a byte-wide Transmit Holding Register (THR). TSR shifts out every data bit with the 16X/8X/4X internal clock. A bit time is 16 (8 if 8X or 4 if 4X) clock periods (see DLD[5:4]). The transmitter sends the startbit 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[6:5]). 13 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.9.1 REV. 1.0.2 Transmit Holding Register (THR) - Write Only The transmit holding register is an 8-bit register providing a data interface to the host processor. The host writes transmit data byte to the THR to be converted into a serial data stream including start-bit, data bits, parity-bit and stop-bit(s). The least-significant-bit (Bit-0) becomes first data bit to go out. The THR is the input register to the transmit FIFO of 64 bytes when FIFO operation is enabled by FCR bit-0. Every time a write operation is made to the THR, the FIFO data pointer is automatically bumped to the next sequential data location. 2.9.2 Transmitter Operation in non-FIFO Mode The host loads transmit data to THR one character at a time. The THR empty flag (LSR bit-5) is set when the data byte is transferred to TSR. THR flag can generate a transmit empty interrupt (ISR bit-1) when it is enabled by IER bit-1. The TSR flag (LSR bit-6) is set when TSR becomes completely empty. FIGURE 6. TRANSMITTER OPERATION IN NON-FIFO MODE Transmit Holding Register (THR) Data Byte 16X or 8X or 4X Clock ( DLD[5:4] ) THR Interrupt (ISR bit-1) Enabled by IER bit-1 Transmit Shift Register (TSR) M S B L S B TXNOFIFO1 2.9.3 Transmitter Operation in FIFO Mode The host may fill the transmit FIFO with up to 64 bytes of transmit data. The THR empty flag (LSR bit-5) is set whenever the FIFO is empty. The THR empty flag can generate a transmit empty interrupt (ISR bit-1) when the amount of data in the FIFO falls below its programmed trigger level. The transmit empty interrupt is enabled by IER bit-1. The TSR flag (LSR bit-6) is set when TSR/FIFO becomes empty. FIGURE 7. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE Transmit Data Byte Transmit FIFO THR Interrupt (ISR bit-1) falls below the programmed Trigger Level and then when becomes empty. FIFO is Enabled by FCR bit-0=1 Auto CTS Flow Control (CTS# pin) Flow Control Characters (Xoff1/2 and Xon1/2 Reg.) Auto Software Flow Control 16X or 8X or 4X Clock ( DLD[5:4] ) Transm it Data Shift Register (TSR) TXFIFO 1 14 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 2.10 Receiver The receiver section contains an 8-bit Receive Shift Register (RSR) and 64 bytes of FIFO which includes a byte-wide Receive Holding Register (RHR). The RSR uses the 16X/8X/4X clock (DLD [5:4]) 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/4X clock rate. After 8 clocks (or 4 if 8X or 2 if 4X) 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. 2.10.1 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. FIGURE 8. RECEIVER OPERATION IN NON-FIFO MODE 16X or 8X or 4X C lock ( D LD[5:4] ) R eceive D ata B yte and E rrors R eceive D ata S hift R egister (R S R ) E rror Tags in LS R bits 4:2 R eceive D ata H olding R egister (R H R) D ata Bit V alidation R eceive D ata C haracters R H R Interrupt (ISR bit-2) R XFIFO 1 15 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 9. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE 16X or 8X or 4X Clock ( DLD[5:4] ) Receive Data Shift Register (RSR) Data Bit Validation 64 bytes by 11-bit wide FIFO Error Tags (64-sets) Data falls to Resume Level Receive Data FIFO FIFO Trigger=16 Error Tags in LSR bits 4:2 Data fills to Halt Level Receive Data Byte and Errors Receive Data Characters Example : - RX FIFO trigger level selected at 16 bytes (See Note Below) RTS# re-asserts when data falls to the Resume Level to restart remote transmitter. Enable by EFR bit-6=1, MCR bit-1. 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 to the Halt Level to suspend remote transmitter. Enable by EFR bit-6=1, MCR bit-1. Receive Data RXFIFO1 2.11 Auto RTS (Hardware) Flow Control 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. 2.12 Auto RTS Halt and Resume The RTS# pin will not be forced HIGH (RTS off) until the receive FIFO reaches the Halt Level (TCR[3:0]). The RTS# pin will return LOW after the RX FIFO is unloaded to the Resume Level (TCR[7:4]). Under these conditions, the M752 will continue to accept data if the remote UART continues to transmit data. It is the responsibility of the user to ensure that the Halt Level is greater than the Resume Level. If interrupts are used, it is recommended that Halt Level > RX Trigger Level > Resume Level. The Auto RTS function is initiated when the RTS# output pin is asserted LOW (RTS On). 2.13 Auto RS485 Half-duplex Control The auto RS485 half-duplex direction control changes the behavior of the transmitter when enabled by DLD bit-6. It also changes the behavior of the transmit empty interrupt (see Table 4). When idle, the auto RS485 half-duplex direction control signal (RTS#) is LOW for receive mode. When data is loaded into the THR for transmission, the RTS# output is automatically asserted HIGH prior to sending the data. After the last stop bit of the last character that has been transmitted, the RTS# signal is automatically de-asserted. 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, it only has to load data bytes to the transmit FIFO. The transmitter automatically reasserts RTS# (HIGH) output prior to sending the data. 16 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 2.14 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. FIGURE 10. AUTO RTS AND CTS FLOW CONTROL OPERATION Local UART UARTA Remote UART UARTB RXA Receiver FIFO Trigger Reached RTSA# Auto RTS Trigger Level Receiver FIFO Trigger Reached RTSB# Assert RTS# to Begin Transmission 1 ON Auto RTS Trigger Level 10 OFF ON 7 2 CTSB# Auto CTS Monitor RXB CTSA# Auto CTS Monitor Transmitter CTSB# TXA Transmitter RTSA# TXB ON 3 8 OFF 6 Suspend 11 ON TXB Data Starts 4 Restart 9 RXA FIFO INTA (RXA FIFO Interrupt) Receive RX FIFO Data Trigger Level 5 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 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 2.15 REV. 1.0.2 Auto Xon/Xoff (Software) Flow Control When software flow control is enabled (See Table 15), the M752 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 M752 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 M752 will monitor the receive data stream for a match to the Xon-1,2 character. If a match is found, the M752 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 M752 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 M752 automatically sends the Xoff-1,2 via the serial TX output to the remote modem when the RX FIFO reaches the Halt Level (TCR[3:0]). To clear this condition, the M752 will transmit the programmed Xon-1,2 characters as soon as RX FIFO falls down to the Resume Level. 2.16 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 M752 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. 2.17 Infrared Mode The M752 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 HIGHpulse 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 DLD register bit-7 to a ‘1’. When the infrared feature is enabled, the transmit data output, TX, idles LOW. Likewise, the RX input also idles LOW, see Figure 11. 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. 18 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 11. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING Character TX Data 0 1 0 1 0 Stop Start Data Bits 1 0 1 1 0 Transmit IR Pulse (TX Pin) 1/2 Bit Time Bit Time 3/16 Bit Time IrEncoder-1 Receive IR Pulse (RX pin) Bit Time 1/16 Clock Delay 1 0 1 0 0 1 1 0 Data Bits 1 Stop 0 Start RX Data Character IRdecoder- 2.18 Sleep Mode with Auto Wake-Up The M752 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 M752 to enter sleep mode: ■ no interrupts pending for both channels of the M752 (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 M752 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 M752 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 M752 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 M752 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 M752 will stay in the sleep mode of operation until it is disabled by setting IER bit-4 to a logic 0. 19 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 If the address lines, data bus lines, IOW#, IOR#, CSA#, CSB#, and modem input lines remain steady when the M752 is in sleep mode, the maximum current will be in the microamp range as specified in the DC Electrical Characteristics on page 38. If the input lines are floating or are toggling while the M752 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 M752 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. 2.19 Internal Loopback The M752 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. 20 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 12. INTERNAL LOOP BACK IN CHANNEL A AND B VCC TXA/TXB Transmit Shift Register (THR/FIFO) Receive Shift Register (RHR/FIFO) RXA/RXB VCC RTSA#/RTSB# RTS# Modem / General Purpose Control Logic Internal Data Bus Lines and Control Signals MCR bit-4=1 CTS# CTSA#/CTSB# VCC DTRA#/DTRB# DTR# DSR# DSRA#/DSRB# OP1# RI# VCC RIA#/RIB# OP2A#/OP2B# OP2# CD# CDA#/CDB# 21 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 3.0 UART INTERNAL REGISTERS Each of the UART channel in the M752 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 CHANNEL A AND B UART INTERNAL REGISTERS ADDRESSES A2 A1 A0 REGISTER READ/WRITE COMMENTS LCR[7] = 0 16C550 COMPATIBLE REGISTERS 0 0 0 RHR - Receive Holding Register THR - Transmit Holding Register Read-only Write-only 0 0 0 DLL - Divisor LSB Read/Write 0 0 1 DLM - Divisor MSB Read/Write 0 1 0 DLD - Divisor Fractional Read/Write 0 0 1 IER - Interrupt Enable Register Read/Write 0 1 0 ISR - Interrupt Status Register FCR - FIFO Control Register Read-only Write-only 0 1 1 LCR - Line Control Register Read/Write 1 0 0 MCR - Modem Control Register Read/Write 1 0 1 LSR - Line Status Register Read-only 1 1 0 MSR - Modem Status Register Read-only See Table 13 1 1 1 SPR - Scratch Pad Register Read/Write See Table 12 1 1 0 TCR - Transmission Control Register Read/Write See Table 13 1 1 1 TLR - Trigger Level Register Read/Write See Table 12 1 1 1 FIFO Rdy - FIFO Ready Register Read-only See Table 12 LCR[7] = 1, LCR ≠ 0xBF LCR[7] = 1, LCR ≠ 0xBF, EFR[4] = 1 LCR[7] = 0 LCR ≠ 0xBF ENHANCED REGISTERS 0 1 0 EFR - Enhanced Function Register Read/Write 1 0 0 Xon-1 - Xon Character 1 Read/Write 1 0 1 Xon-2 - Xon Character 2 Read/Write 1 1 0 Xoff-1 - Xoff Character 1 Read/Write 1 1 1 Xoff-2 - Xoff Character 2 Read/Write 22 LCR = 0xBF XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 . TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1 REG ADDRESS NAME A2-A0 READ/ WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT 16C550 Compatible Registers 000 RHR RD Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 000 THR WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 001 IER RD/WR 0/ 0/ 0/ 0/ CTS Int. Enable RTS Int. Enable Xoff Int. Enable Sleep Mode Enable 0/ 0/ INT Source Bit-5 INT Source Bit-4 0/ 0/ 010 010 ISR FCR RD WR FIFOs FIFOs Enabled Enabled RX FIFO RX FIFO Trigger Trigger TX FIFO TX FIFO Trigger Trigger 011 LCR RD/WR Divisor Enable Set TX Break Set Parity 100 MCR RD/WR 0/ 0/ 0/ Clock Prescaler Select Even Parity Modem RX Line Stat. Int. Stat. Int. Enable Enable TX RX Data Empty Int. Int Enable Enable INT Source Bit-3 INT Source Bit-2 INT Source Bit-1 INT Source Bit-0 DMA TX FIFO Mode Reset Enable RX FIFO Reset FIFOs Enable Parity Enable Word Length Bit-1 Word Length Bit-0 RTS# Output Control DTR# Output Control Stop Bits Internal OP2#/ FIFO Lopback INT OutRdy TCR and XonAny Enable Enable put TLR Enable (OP1#) ENable LCR[7]=0 LCR≠0xBF 101 LSR RD RX FIFO Global Error THR & TSR Empty THR Empty RX Break RX Framing Error RX Parity Error RX Overrun Error RX Data Ready 110 MSR RD CD# Input RI# Input DSR# Input CTS# Input Delta CD# Delta RI# Delta DSR# Delta CTS# See Table 13 111 SPR RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 See Table 12 110 TCR RD/WR Resume Resume Resume Resume Bit-3 Bit-2 Bit-1 Bit-0 Halt Bit-3 Halt Bit-2 Halt Bit-1 Halt Bit-0 See Table 13 111 TLR RD/WR RX Trig Bit-3 TX Trig Bit-3 TX Trig Bit-2 TX Trig Bit-1 111 FIFO Rdy 0 0 RD 0 RX Trig Bit-2 0 RX Trig Bit-1 RX Trig Bit-0 RX FIFO RX FIFO B Status A Status 23 TX Trig See Table 12 Bit-0 TX FIFO TX FIFO See Table 12 B Status A Status XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 TABLE 8: INTERNAL REGISTERS DESCRIPTION. SHADED BITS ARE ENABLED WHEN EFR BIT-4=1 REG ADDRESS NAME A2-A0 READ/ WRITE BIT-7 BIT-6 BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 COMMENT LCR[7]=1 LCR≠0xBF Baud Rate Generator Divisor 000 DLL RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 001 DLM RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 010 DLD RD/WR IR Mode Bit-3 Bit-2 Bit-1 Bit-0 Software Flow Cntl Bit-2 Software Flow Cntl Bit-1 Software Flow Cntl Bit-0 DLD Software Flow Cntl Bit-3 Auto 4X Mode 8X Mode RS485 Direction Control LCR[7]=1 LCR≠0xBF EFR[4]=1 Enhanced Registers 010 EFR RD/WR Auto Auto RTS CTS Enable Enable Special Char Select Enable IER [7:4], ISR [5:4], FCR[5:4], MCR[7:5], 100 XON1 RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 101 XON2 RD/WR Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 110 XOFF RD/WR 1 Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 111 XOFF RD/WR 2 Bit-7 Bit-6 Bit-5 Bit-4 Bit-3 Bit-2 Bit-1 Bit-0 LCR=0XBF 4.0 INTERNAL REGISTER DESCRIPTIONS 4.1 Receive Holding Register (RHR) - Read- Only SEE”RECEIVER” ON PAGE 15. 4.2 Transmit Holding Register (THR) - Write-Only SEE”TRANSMITTER” ON PAGE 13. 4.3 Interrupt Enable Register (IER) - Read/Write The Interrupt Enable Register (IER) masks the interrupts from receive data ready, transmit empty, line status and modem status registers. These interrupts are reported in the Interrupt Status Register (ISR). 4.3.1 IER versus Receive FIFO Interrupt Mode Operation When the receive FIFO (FCR BIT-0 = 1) and receive interrupts (IER BIT-0 = 1) are enabled, the RHR interrupts (see ISR bits 2 and 3) status will reflect the following: A. The receive data available interrupts are issued to the host when the FIFO has reached the programmed trigger level. It will be cleared when the FIFO drops below the programmed trigger level. B. FIFO level will be reflected in the ISR register when the FIFO trigger level is reached. Both the ISR register status bit and the interrupt will be cleared when the FIFO drops below the trigger level. C. The receive data ready bit (LSR BIT-0) is set as soon as a character is transferred from the shift register to the receive FIFO. It is reset when the FIFO is empty. 24 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 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 XR16M752 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 spaces in the FIFO is above 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, 4 or 7 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 bit-7 is set if any character in the RX FIFO has a parity or framing error, or is a break character. LSR[4:2] always show the error status for the received character available for reading from the RX FIFO. If IER[2] = 1, an LSR interrupt will be generated as long as LSR[7] = 1, ie. the RX FIFO contains at lease one character with an error. • 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. IER[4]: Sleep Mode Enable (requires EFR bit-4 = 1) • Logic 0 = Disable Sleep Mode (default). • Logic 1 = Enable Sleep Mode. See Sleep Mode section for further details. IER[5]: Xoff Interrupt Enable (requires EFR bit-4=1) • Logic 0 = Disable the software flow control, receive Xoff interrupt (default). • Logic 1 = Enable the receive Xoff interrupt. See Software Flow Control section for details. 25 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 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, 4 and 7. • 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 reading all characters with errors out of the RX FIFO. • 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 when Xon character(s) is received. • Special character interrupt is cleared by a read to ISR. • RTS# and CTS# flow control interrupts are cleared by a read to the MSR register. 26 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 ] TABLE 9: INTERRUPT SOURCE AND PRIORITY LEVEL PRIORITY ISR REGISTER STATUS BITS SOURCE OF INTERRUPT LEVEL BIT-5 BIT-4 BIT-3 BIT-2 BIT-1 BIT-0 1 0 0 0 1 1 0 LSR (Receiver Line Status Register) 2 0 0 1 1 0 0 RXRDY (Receive Data Time-out) 3 0 0 0 1 0 0 RXRDY (Received Data Ready) 4 0 0 0 0 1 0 TXRDY (Transmit Ready) 5 0 0 0 0 0 0 MSR (Modem Status Register) 6 0 1 0 0 0 0 RXRDY (Received Xoff or Special character) 7 1 0 0 0 0 0 CTS#, RTS# change of state - 0 0 0 0 0 1 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 is cleared when XON is received. If it is a special character interrupt, it is cleared by reading ISR. 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. 27 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 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. FCR[2]: TX FIFO Reset This bit is only active when FCR bit-0 is a ‘1’. • Logic 0 = No transmit FIFO reset (default). • Logic 1 = Reset the transmit FIFO pointers and FIFO level counter logic (the transmit shift register is not cleared or altered). This bit will return to a logic 0 after resetting the FIFO. FCR[3]: 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 spaces in the FIFO is above 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 shows the selections. The UART will issue a transmit interrupt when the number of available spaces in the FIFO is less than the transmit trigger level. Table 10 shows the selections. FCR[7:6]: Receive FIFO Trigger Select (logic 0 = default, RX trigger level =1) 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 is greater than the receive trigger level or when a receive data timeout occurs (see “Section 2.10, Receiver” on page 15). TABLE 10: TRANSMIT AND RECEIVE FIFO TRIGGER LEVEL SELECTION FCR BIT-7 0 0 1 1 FCR BIT-6 FCR BIT-5 FCR BIT-4 0 0 1 1 0 1 0 1 RECEIVE TRIGGER LEVEL (CHARACTERS) TRANSMIT TRIGGER LEVEL (SPACES) 8 16 32 56 0 1 0 1 8 16 56 60 28 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 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 BIT-0 WORD LENGTH 0 0 5 0 1 6 (default) 1 0 7 1 1 8 LCR[2]: TX and RX Stop-bit Length Select The length of stop bit is specified by this bit in conjunction with the programmed word length. LENGTH STOP BIT LENGTH (BIT TIME(S)) 0 5,6,7,8 1 1 5 1-1/2 1 6,7,8 2 (default) BIT-2 WORD 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. • 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. 29 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 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 PARITY SELECTION X X 0 No parity 0 0 1 Odd parity 0 1 1 Even parity 1 0 1 Force parity to mark, “1” 1 1 1 Forced parity to space, “0” LCR[6]: Transmit Break Enable When enabled, the Break control bit causes a break condition to be transmitted (the TX output is forced to a “space", LOW state). This condition remains, until disabled by setting LCR bit-6 to a logic 0. • Logic 0 = No TX break condition (default). • Logic 1 = Forces the transmitter output (TX) to a “space”, LOW, for alerting the remote receiver of a line break condition. LCR[7]: Baud Rate Divisors Enable Baud rate generator divisor (DLL, DLM and DLD) enable. • Logic 0 = Data registers are selected (default). • Logic 1 = Divisor latch registers are selected. 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. 30 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 MCR[2]: OP1# / FIFO Rdy Enable OP1# is not available as an output pin on the M752. But it is available for use during Internal Loopback Mode (MCR[4] = 1). In the Internal Loopback Mode, this bit is used to write the state of the modem RI# interface signal. This bit is also used to select between the SPR, TLR and FIFO Rdy registers. All of these registers are accessible at address offset 0x7 when LCR≠0xBF. However, LCR = 0xBF is required to access EFR. TABLE 12: REGISTER AT ADDRESS OFFSET 0X7 EFR[4] MCR[6] MCR[4, 2] Register at Address Offset 0x7 0 X ≠’01’ Scratchpad Register (SPR) 1 0 ≠’01’ Scratchpad Register (SPR) 1 1 ≠’01’ Trigger Level Register (TLR) X X =’01’ FIFO Ready Register (FIFO Rdy) 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 to write to this bit) • 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 M752 is programmed to use the Xon/Xoff flow control. MCR[6]: TCR and TLR Enable (requires EFR bit-4=1 to write to this bit) This bit enables the TCR and TLR registers at address offset 0x6 and 0x7, respectively. See Table 12 above for the correct register setting to access the TLR register. See Table 13 below for the setting to access the TCR register. • Logic 0 = Reserved (default). • Logic 1 = Enable access to the TCR and TLR registers. TABLE 13: REGISTER AT ADDRESS OFFSET 0X6 EFR[4] MCR[6] Register at Address Offset 0x6 0 X Modem Status Register (MSR) 1 0 Modem Status Register (MSR) 1 1 Trigger Control Register (TCR) 31 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 MCR[7]: Clock Prescaler Select (requires EFR bit-4=1 to write to this bit) • 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. 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). 32 XR16M752/XR68M752 REV. 1.0.2 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO • 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. 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. 33 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 4.10 REV. 1.0.2 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. There are also two other registers (TLR and FIFO Rdy) that share the same address location as the Scratch Pad Register. See Table 12. 4.11 Transmission Control Register (TCR) - Read/Write (requires EFR bit-4 = 1) This register replaces MSR and is accessible only when MCR[6] = 1. This 8-bit register is used to store the RX FIFO threshold levels to halt/resume transmission during hardware or software flow control. TCR[3:0]: RX FIFO Halt Level A value of 0-60 (decimal value of TCR[3:0] multiplied by 4) can be selected as the Halt Level. When the RX FIFO is greater than or equal to this value, the RTS# output will be de-asserted if Auto RTS flow control is used or the XOFF character(s) will be transmitted if Auto XON/XOFF flow control is used. It is recommended that this value is greater than the RX Trigger Level. TCR[7:4]: RX FIFO Resume Level A value of 0-60 (decimal value of TCR[7:4] multiplied by 4) can be selected as the Resume Level. When the RX FIFO is less than or equal to this value, the RTS# output will be re-asserted if Auto RTS flow control is used or the XON character(s) will be transmitted if Auto XON/XOFF flow control is used. It is recommended that this value is less than the RX Trigger Level. 4.12 Trigger Level Register (TLR) - Read/Write (requires EFR bit-4 = 1) This register replaces SPR and is accessible under the conditions listed in Table 12. This 8-bit register is used to store the RX and TX FIFO trigger levels used for interrupts. TLR[3:0]: TX FIFO Trigger Level A value of 4-60 (decimal value of TCR[3:0] multiplied by 4) can be selected as the TX FIFO Trigger Level. When the number of available spaces in the TX FIFO is greater than or equal to this value, a Transmit Ready interrupt is generated. For any non-zero value, TCR[3:0] will be used as the TX FIFO Trigger Level. If TCR[3:0] = 0x0, then the TX FIFO Trigger Level is the value selected by FCR[5:4]. See Table 10. TLR[7:4]: RX FIFO Trigger Level A value of 4-60 (decimal value of TCR[7:4] multiplied by 4) can be selected as the RX FIFO Trigger Level. When the number of characters received in the RX FIFO is greater than or equal to this value, a Receive Data Ready interrupt is generated (a Receive Data Timeout interrupt is independent of the RX FIFO Trigger Level and can be generated any time there is at least 1 byte in the RX FIFO and the RX input has been idle for the timeout period described in “Section 2.10, Receiver” on page 15). For any non-zero value, TCR[7:4] will be used as the RX FIFO Trigger Level. If TCR[7:4] = 0x0, then the RX FIFO Trigger Level is the value selected by FCR[7:6]. See Table 10. 4.13 Baud Rate Generator Registers (DLL, DLM and DLD[3:0]) - 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[3:0]/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. DLD[5:4]: Sampling Rate Select These bits select the data sampling rate. By default, the data sampling rate is 16X. The maximum data rate will double if the 8X mode is selected and will quadruple if the 4X mode is selected. See Table 14 below. 34 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 TABLE 14: SAMPLING RATE SELECT DLD[5] DLD[4] SAMPLING RATE 0 0 16X 0 1 8X 1 X 4X DLD[6]: 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. The RTS# output can be used as a general purpose output or for Auto RTS flow control. • Logic 1 = Enable Auto RS485 Direction Control function. The direction control signal, RTS# pin, changes its output logic state from HIGH to LOW 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 HIGH when a data byte is loaded into the TX FIFO. See “Section 2.13, Auto RS485 Half-duplex Control” on page 16. DLD[7]: Infrared Encoder/Decoder Enable • 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 requirement. While in this mode, the infrared TX output will be idling LOW. SEE”INFRARED MODE” ON PAGE 18. 4.14 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. TABLE 15: SOFTWARE FLOW CONTROL FUNCTIONS EFR BIT-3 CONT-3 EFR BIT-2 CONT-2 EFR BIT-1 CONT-1 EFR BIT-0 CONT-0 0 0 0 0 No TX and RX flow control (default and reset) 0 0 X X No transmit flow control 1 0 X X Transmit Xon1, Xoff1 0 1 X X Transmit Xon2, Xoff2 1 1 X X Transmit Xon1 and Xon2, Xoff1 and Xoff2 X X 0 0 No receive flow control X X 1 0 Receiver compares Xon1, Xoff1 35 TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 TABLE 15: SOFTWARE FLOW CONTROL FUNCTIONS EFR BIT-3 CONT-3 EFR BIT-2 CONT-2 EFR BIT-1 CONT-1 EFR BIT-0 CONT-0 X X 0 1 Receiver compares Xon2, Xoff2 1 0 1 1 Transmit Xon1, Xoff1 Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 0 1 1 1 Transmit Xon2, Xoff2 Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 1 1 1 1 Transmit Xon1 and Xon2, Xoff1 and Xoff2, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 0 0 1 1 No transmit flow control, Receiver compares Xon1 and Xon2, Xoff1 and Xoff2 TRANSMIT AND RECEIVE SOFTWARE FLOW CONTROL EFR[4]: Enhanced Function Bits Enable Enhanced function control bit. This bit enables IER bits 4-7, ISR bits 4-5, FCR bits 4-5, MCR bits 5-7, TCR, TLR 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. 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 programmed HALT level. RTS# will return LOW when FIFO data falls below the programmed RESUME 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). 36 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 • Logic 1 = Enable Automatic CTS flow control. Data transmission stops when CTS# input de-asserts HIGH. Data transmission resumes when CTS# returns LOW. 4.14.1 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 8. TABLE 16: UART RESET CONDITIONS FOR CHANNEL A AND B REGISTERS RESET STATE DLM, DLL DLM = 0x00 and DLL = 0x01. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. DLD Bits 7-0 = 0x00 RHR Bits 7-0 = 0xXX THR Bits 7-0 = 0xXX IER Bits 7-0 = 0x00 FCR Bits 7-0 = 0x00 ISR Bits 7-0 = 0x01 LCR Bits 7-0 = 0x1D MCR Bits 7-0 = 0x00 LSR Bits 7-0 = 0x60 MSR Bits 3-0 = Logic 0 Bits 7-4 = Logic levels of the inputs inverted SPR Bits 7-0 = 0xFF. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. TCR Bits 7-0 = 0x0F TLR Bits 7-0 = 0x00 FIFO Rdy Bits 7-0 = 0x03 EFR Bits 7-0 = 0x00 XON1 Bits 7-0 = 0x00. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. XON2 Bits 7-0 = 0x00. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. XOFF1 Bits 7-0 = 0x00. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. XOFF2 Bits 7-0 = 0x00. Only resets to these values during a power up. They do not reset when the Reset Pin is asserted. 37 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 TABLE 16: UART RESET CONDITIONS FOR CHANNEL A AND B REGISTERS RESET STATE I/O SIGNALS RESET STATE TX HIGH OP2# HIGH RTS# HIGH DTR# HIGH RXRDY# HIGH TXRDY# LOW INT Three-State Condition 5.0 ELECTRICAL CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS Power Supply Range 4 Volts Voltage at Any Pin GND-0.3V to 4V Operating Temperature -40o to +85oC Storage Temperature -65o to +150oC Package Dissipation 500 mW TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: ± 15%) Thermal Resistance (48-TQFP) theta-ja =59oC/W, theta-jc = 16oC/W Thermal Resistance (32-QFN) theta-ja = 33oC/W, theta-jc = 22oC/W DC ELECTRICAL CHARACTERISTICS TA= -40o to +85oC, Vcc is 1.62V to 3.63V SYMBOL PARAMETER LIMITS 1.8V MIN MAX LIMITS 2.5V MIN MAX LIMITS 3.3V MIN MAX UNITS VILCK Clock Input Low Level -0.3 0.3 -0.3 0.6 -0.3 0.6 V VIHCK Clock Input High Level 1.4 VCC 1.8 VCC 2.4 VCC V VIL Input Low Voltage -0.3 0.2 -0.3 0.5 -0.3 0.8 V VIH Input High Voltage 1.4 VCC 1.8 VCC 2.0 VCC V VOL Output Low Voltage 0.4 V V 0.4 0.4 CONDITIONS IOL = 4 mA IOL = 2 mA IOL = 1.5 mA 38 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 DC ELECTRICAL CHARACTERISTICS TA= -40o to +85oC, Vcc is 1.62V to 3.63V SYMBOL VOH LIMITS 1.8V MAX MIN PARAMETER LIMITS 2.5V MAX MIN Output High Voltage LIMITS 3.3V MAX MIN 2.0 UNITS V V 1.8 CONDITIONS IOH = -1 mA IOH = -400 uA 1.4 IOH = -200 uA IIL Input Low Leakage Current ±10 ±10 ±10 uA IIH Input High Leakage Current ±10 ±10 ±10 uA CIN Input Pin Capacitance 5 5 5 pF ICC Power Supply Current 0.5 1 2 mA XTAL1 = 2 MHz ISLEEP Sleep Current (16 Mode) 3 10 15 uA See Test 1 ISLEEP Sleep Current (68 Mode) 50 75 100 uA See Test 1 Test 1: The following inputs must remain steady at VCC or GND state to minimize Sleep current: A0-A2, D0D7, IOR#, IOW#, CSA# (CS# in 68 Mode), 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. AC ELECTRICAL CHARACTERISTICS Unless otherwise noted: TA=-40o to +85oC, Vcc=1.62 - 3.63V, 70 pF load where applicable SYMBOL LIMITS LIMITS LIMITS 1.8V ± 10% 2.5V ± 10% 3.3V ± 10% MIN MAX MIN MAX MIN MAX PARAMETER UNIT XTAL1 UART Crystal Oscillator 24 24 24 MHz ECLK External Clock 32 50 64 MHz TECLK External Clock Time Period 15 10 7 ns TAS Address Setup Time (16 mode) 5 5 5 ns TAH Address Hold Time (16 mode) 0 0 0 ns TCS Chip Select Width (16 mode) 60 30 30 ns TRD IOR# Strobe Width (16 mode) 60 30 30 ns TDY Read Cycle Delay (16 mode) 60 30 30 ns TRDV Data Access Time (16 mode) TDD Data Disable Time (16 mode) 0 TWR IOW# Strobe Width (16 mode) 60 30 30 ns TDY Write Cycle Delay (16 mode) 60 30 30 ns TDS Data Setup Time (16 mode) 15 10 10 ns 55 39 20 25 0 20 0 25 ns 10 ns XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 AC ELECTRICAL CHARACTERISTICS Unless otherwise noted: TA=-40o to +85oC, Vcc=1.62 - 3.63V, 70 pF load where applicable SYMBOL LIMITS LIMITS LIMITS 1.8V ± 10% 2.5V ± 10% 3.3V ± 10% MIN MAX MIN MAX MIN MAX PARAMETER UNIT TDH Data Hold Time (16 mode) 5 5 5 ns TADS Address Setup (68 Mode) 5 5 5 ns TADH Address Hold (68 Mode) 0 0 0 ns TRWS R/W# Setup to CS# (68 Mode) 5 5 5 ns TRDA Read Data Access (68 mode) 55 25 25 ns TRDH Read Data Disable (68 mode) 20 20 10 ns TWDS Write Data Setup (68 mode) 15 10 10 ns TWDH Write Data Hold (68 Mode) 5 5 5 ns TRWH CS# De-asserted to R/W# De-asserted (68 Mode) 5 5 5 ns TCSL CS# Width (68 Mode) 60 30 30 ns TCSD CS# Cycle Delay (68 Mode) 60 30 30 ns TWDO Delay From IOW# To Output 50 50 50 ns TMOD Delay To Set Interrupt From MODEM Input 50 50 50 ns TRSI Delay To Reset Interrupt From IOR# 50 50 50 ns TSSI Delay From Stop To Set Interrupt 1 1 1 Bclk TRRI Delay From IOR# To Reset Interrupt 45 45 45 ns TSI Delay From Stop To Interrupt 45 45 45 ns TINT Delay From Initial INT Reset To Transmit Start 24 Bclk TWRI Delay From IOW# To Reset Interrupt 45 45 45 ns TSSR Delay From Stop To Set RXRDY# 1 1 1 Bclk TRR Delay From IOR# To Reset RXRDY# 45 45 45 ns TWT Delay From IOW# To Set TXRDY# 45 45 45 ns TSRT Delay From Center of Start To Reset TXRDY# 8 8 8 Bclk TRST Reset Pulse Width Bclk Baud Clock 8 40 40 24 8 40 24 8 40 ns 16X or 8X or 4X of data rate Hz XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 13. CLOCK TIMING TECLK TECL TECH 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# Change of state Change of state T MO D T M OD INT Active Active Active T RSI IOR# Active Active Active T M OD Change of state RI# 41 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 15. 16 MODE (INTEL) DATA BUS READ TIMING A0-A2 Valid Address TAS TCS Valid Address TAS TAH TAH TCS CSA#/ CSB# TDY TRD TRD IOR# TDD TRDV D0-D7 TDD TRDV Valid Data Valid Data RDTm FIGURE 16. 16 MODE (INTEL) DATA BUS WRITE TIMING A0-A2 Valid Address TAS TCS Valid Address TAS TAH TCS TAH CSA#/ CSB# TDY TWR TWR IOW# TDS D0-D7 TDH Valid Data TDS TDH Valid Data 16Write 42 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 17. 68 MODE (MOTOROLA) DATA BUS READ TIMING A0-A2 Valid Address TADS TCSL Valid Address TADH CS# TCSD TRWS TRWH R/W# TRDH TRDA D0-D7 Valid Data Valid Data 68Read FIGURE 18. 68 MODE (MOTOROLA) DATA BUS WRITE TIMING A0-A2 Valid Address TADS TCSL Valid Address TADH CS# TCSD TRWS TRWH R/W# TWDS D0-D7 T WDH Valid Data Valid Data 68Write 43 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 19. RECEIVE READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B RX Start Bit Stop Bit D0:D7 INT D0:D7 D0:D7 TSSR TSSR TSSR 1 Byte in RHR 1 Byte in RHR 1 Byte in RHR TSSR TSSR Active Data Ready Active Data Ready RXRDY# TRR TSSR Active Data Ready TRR TRR IOR# (Reading data out of RHR) RXNFM FIGURE 20. TRANSMIT READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B TX Start Bit IER[1] enabled Stop Bit D0:D7 D0:D7 ISR is read D0:D7 ISR is read ISR is read INT* TWRI TWRI TWRI TSRT TSRT 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. 44 TXNonFIFO XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 21. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA DISABLED] FOR CHANNELS A & B Start Bit RX S D0:D7 S D0:D7 T D0:D7 Stop Bit S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T RX FIFO drops below RX Trigger Level TSSI INT FIFO Empties TSSR RX FIFO fills up to RX Trigger Level or RX Data Timeout RXRDY# First Byte is Received in RX FIFO TRRI TRR IOR# (Reading data out of RX FIFO) RXINTDMA# FIGURE 22. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA ENABLED] FOR CHANNELS A & B Start Bit RX Stop Bit S D0:D7 S D0:D7 T D0:D7 S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T RX FIFO drops below RX Trigger Level TSSI INT RX FIFO fills up to RX Trigger Level or RX Data Timeout FIFO Empties TSSR RXRDY# TRRI TRR IOR# (Reading data out of RX FIFO) RXFIFODMA 45 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 FIGURE 23. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE DISABLED] FOR CHANNELS A & B Start Bit TX FIFO Empty TX Stop Bit S D0:D7 T (Unloading) IER[1] enabled Last Data Byte Transmitted T S D0:D7 T S D0:D7 T S D0:D7 T S D0:D7 T ISR is read TSI ISR is read S D0:D7 T TSRT INT* TX FIFO Empty TX FIFO fills up to trigger level Data in TX FIFO TXRDY# TX FIFO drops below trigger level TWRI 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 24. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE ENABLED] FOR CHANNELS A & B Start Bit TX Stop Bit Last Data Byte Transmitted S D0:D7 T S D0:D7 T (Unloading) IER[1] enabled D0:D7 S D0:D7 T ISR Read S D0:D7 T S D0:D7 T S D0:D7 T TSI TSRT ISR Read INT* TX FIFO fills up to trigger level TXRDY# TX FIFO drops below trigger level TWRI At least 1 empty location in FIFO TX FIFO Full TWT IOW# (Loading data into FIFO) *INT cleared when the ISR is read or when TX FIFO fills up to trigger level. 46 TXDMA XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 PACKAGE DIMENSIONS (48 PIN TQFP - 7 X 7 X 1 mm) D D1 36 25 37 24 D1 48 13 1 2 1 B e A2 C A Seating Plane α A1 L Note: The control dimension is the millimeter column INCHES MILLIMETERS SYMBOL MIN MAX MIN MAX A 0.039 0.047 1.00 1.20 A1 0.002 0.006 0.05 0.15 A2 0.037 0.041 0.95 1.05 B 0.007 0.011 0.17 0.27 C 0.004 0.008 0.09 0.20 D 0.346 0.362 8.80 9.20 D1 0.272 0.280 6.90 7.10 e 0.020 BSC 0.50 BSC L 0.018 0.030 0.45 0.75 a 0° 7° 0° 7° 47 D XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 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 MILLIMETERS SYMBOL MIN MAX MIN MAX A 0.031 0.039 0.80 1.00 A1 0.000 0.002 0.00 0.05 A3 0.006 0.010 0.15 0.25 D 0.193 0.201 4.90 5.10 D2 0.138 0.150 3.50 3.80 b 0.007 0.012 0.18 0.30 e 0.0197 BSC 0.50 BSC L 0.012 0.020 0.35 0.45 k 0.008 - 0.20 - 48 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 REVISION HISTORY DATE REVISION DESCRIPTION July 2006 P1.0.0 September 2006 1.0.0 Final Datasheet. Updated AC Electrical Characteristics. May 2007 1.0.1 Corrected pin names pin out assignment for 48-pin TQFP package for XR68M752 in Motorola mode. Added GND center pad for QFN package to pin description. Added Motorola mode Read/Write timing waveforms. Updated QFN package dimensions drawing to show minimum "k" parameter. May 2007 1.0.2 Updated pin description table, correct pin # of RXA in QFN-32 package. Preliminary Datasheet. 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 May 2007. Send your UART technical inquiry with technical details to hotline: [email protected]. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. 49 XR16M752/XR68M752 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO REV. 1.0.2 TABLE OF CONTENTS GENERAL DESCRIPTION ................................................................................................ 1 APPLICATIONS ............................................................................................................................................... 1 FEATURES .................................................................................................................................................... 1 FIGURE 1. XR16M752 BLOCK DIAGRAM .......................................................................................................................................... 1 FIGURE 2. PIN OUT ASSIGNMENT ..................................................................................................................................................... 2 ORDERING INFORMATION................................................................................................................................ 3 PIN DESCRIPTIONS ........................................................................................................ 3 1.0 PRODUCT DESCRIPTION....................................................................................................................... 7 2.0 FUNCTIONAL DESCRIPTIONS............................................................................................................... 8 2.1 CPU INTERFACE................................................................................................................................................. 8 FIGURE 3. XR16M752/XR68M752 DATA BUS INTERCONNECTIONS .................................................................................................. 8 2.2 DEVICE RESET ................................................................................................................................................... 9 2.3 CHANNEL A AND B SELECTION....................................................................................................................... 9 TABLE 1: CHANNEL A AND B SELECT IN 16 MODE ............................................................................................................................ 9 TABLE 2: CHANNEL A AND B SELECT IN 68 MODE ............................................................................................................................ 9 2.4 CHANNEL A AND B INTERNAL REGISTERS ................................................................................................... 9 2.5 DMA MODE........................................................................................................................................................ 10 TABLE 3: TXRDY# AND RXRDY# OUTPUTS IN FIFO AND DMA MODE ........................................................................................... 10 2.6 INTA AND INTB OUTPUTS ............................................................................................................................... 10 TABLE 4: INTA AND INTB PINS OPERATION FOR TRANSMITTER ...................................................................................................... 10 TABLE 5: INTA AND INTB PIN OPERATION FOR RECEIVER ............................................................................................................. 10 2.7 CRYSTAL OSCILLATOR OR EXTERNAL CLOCK INPUT .............................................................................. 11 FIGURE 4. TYPICAL OSCILLATOR CONNECTIONS ............................................................................................................................... 11 2.8 PROGRAMMABLE BAUD RATE GENERATOR WITH FRACTIONAL DIVISOR............................................ 11 FIGURE 5. BAUD RATE GENERATOR ............................................................................................................................................... 12 TABLE 6: TYPICAL DATA RATES WITH A 24 MHZ CRYSTAL OR EXTERNAL CLOCK AT 16X SAMPLING ................................................... 13 2.9 TRANSMITTER .................................................................................................................................................. 13 2.9.1 TRANSMIT HOLDING REGISTER (THR) - WRITE ONLY ........................................................................................... 2.9.2 TRANSMITTER OPERATION IN NON-FIFO MODE .................................................................................................... FIGURE 6. TRANSMITTER OPERATION IN NON-FIFO MODE .............................................................................................................. 2.9.3 TRANSMITTER OPERATION IN FIFO MODE ............................................................................................................. FIGURE 7. TRANSMITTER OPERATION IN FIFO AND FLOW CONTROL MODE ..................................................................................... 14 14 14 14 14 2.10 RECEIVER ....................................................................................................................................................... 15 2.10.1 RECEIVE HOLDING REGISTER (RHR) - READ-ONLY ............................................................................................ 15 FIGURE 8. RECEIVER OPERATION IN NON-FIFO MODE .................................................................................................................... 15 FIGURE 9. RECEIVER OPERATION IN FIFO AND AUTO RTS FLOW CONTROL MODE ......................................................................... 16 2.11 AUTO RTS (HARDWARE) FLOW CONTROL ................................................................................................ 2.12 AUTO RTS HALT AND RESUME................................................................................................................... 2.13 AUTO RS485 HALF-DUPLEX CONTROL ..................................................................................................... 2.14 AUTO CTS FLOW CONTROL ........................................................................................................................ 16 16 16 17 FIGURE 10. AUTO RTS AND CTS FLOW CONTROL OPERATION ....................................................................................................... 17 2.15 AUTO XON/XOFF (SOFTWARE) FLOW CONTROL...................................................................................... 18 2.16 SPECIAL CHARACTER DETECT .................................................................................................................. 18 2.17 INFRARED MODE ........................................................................................................................................... 18 FIGURE 11. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING .......................................................................... 19 2.18 SLEEP MODE WITH AUTO WAKE-UP.......................................................................................................... 19 2.19 INTERNAL LOOPBACK ................................................................................................................................. 20 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 ............................................................................... 24 4.3.2 IER VERSUS RECEIVE/TRANSMIT FIFO POLLED MODE OPERATION .................................................................. 25 4.4 INTERRUPT STATUS REGISTER (ISR) - READ-ONLY .................................................................................. 26 4.4.1 INTERRUPT GENERATION: ........................................................................................................................................ 26 I XR16M752/XR68M752 REV. 1.0.2 HIGH PERFORMANCE DUART WITH 64-BYTE FIFO 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 LEVEL SELECTION ............................................................................................ 28 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 . 30 TABLE 12: REGISTER AT ADDRESS OFFSET 0X7 ............................................................................................................................. 31 TABLE 13: REGISTER AT ADDRESS OFFSET 0X6 ............................................................................................................................. 31 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 TRANSMISSION CONTROL REGISTER (TCR) - READ/WRITE (REQUIRES EFR BIT-4 = 1) .................... 4.12 TRIGGER LEVEL REGISTER (TLR) - READ/WRITE (REQUIRES EFR BIT-4 = 1) ...................................... 4.13 BAUD RATE GENERATOR REGISTERS (DLL, DLM AND DLD[3:0]) - READ/WRITE................................ 32 33 34 34 34 34 TABLE 14: SAMPLING RATE SELECT ............................................................................................................................................... 35 4.14 ENHANCED FEATURE REGISTER (EFR) ..................................................................................................... 35 TABLE 15: SOFTWARE FLOW CONTROL FUNCTIONS ........................................................................................................................ 35 4.14.1 SOFTWARE FLOW CONTROL REGISTERS (XOFF1, XOFF2, XON1, XON2) - READ/WRITE .............................. 37 TABLE 16: UART RESET CONDITIONS FOR CHANNEL A AND B ............................................................................................ 37 5.0 ELECTRICAL CHARACTERISTICS ..................................................................................................... ABSOLUTE MAXIMUM RATINGS .................................................................................................................... TYPICAL PACKAGE THERMAL RESISTANCE DATA (MARGIN OF ERROR: ± 15%).............................................. DC ELECTRICAL CHARACTERISTICS............................................................................................................. AC ELECTRICAL CHARACTERISTICS ............................................................................................................. 38 38 38 38 39 FIGURE 13. CLOCK TIMING............................................................................................................................................................. 41 FIGURE 14. MODEM INPUT/OUTPUT TIMING FOR CHANNELS A & B ................................................................................................. 41 FIGURE 16. 16 MODE (INTEL) DATA BUS WRITE TIMING ................................................................................................................. 42 FIGURE 15. 16 MODE (INTEL) DATA BUS READ TIMING ................................................................................................................... 42 FIGURE 17. 68 MODE (MOTOROLA) DATA BUS READ TIMING .......................................................................................................... 43 FIGURE 18. 68 MODE (MOTOROLA) DATA BUS WRITE TIMING ......................................................................................................... 43 FIGURE 19. RECEIVE READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B ......................................................... 44 FIGURE 20. TRANSMIT READY & INTERRUPT TIMING [NON-FIFO MODE] FOR CHANNELS A & B ....................................................... 44 FIGURE 21. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA DISABLED] FOR CHANNELS A & B........................................ 45 FIGURE 22. RECEIVE READY & INTERRUPT TIMING [FIFO MODE, DMA ENABLED] FOR CHANNELS A & B......................................... 45 FIGURE 23. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE DISABLED] FOR CHANNELS A & B ........................... 46 FIGURE 24. TRANSMIT READY & INTERRUPT TIMING [FIFO MODE, DMA MODE ENABLED] FOR CHANNELS A & B ............................ 46 PACKAGE DIMENSIONS (48 PIN TQFP - 7 X 7 X 1 mm) .................................................................................. 47 PACKAGE DIMENSIONS (32 PIN QFN - 5 X 5 X 0.9 mm) ............................................................................... 48 REVISION HISTORY ..................................................................................................................................... 49 TABLE OF CONTENTS ..................................................................................................... I II