XR17C158CV-F Exar Corporation, XR17C158CV-F Datasheet - Page 27

• Manufacturer Part Number: XR17C158CV-F
• Description: IC UART PCI BUS 5V OCTAL 144LQFP
• Manufacturer: Exar Corporation
• Type: Universal PCI Bus Octal UARTr

Specifications of XR17C158CV-F

• Number Of Channels: 8
• Package / Case: 144-LQFP
• Features: *
• Fifo's: 64 Byte
• Protocol: RS485
• Voltage - Supply: 5V
• With Auto Flow Control: Yes
• With Irda Encoder/decoder: Yes
• With False Start Bit Detection: Yes
• With Modem Control: Yes
• Mounting Type: Surface Mount
• Data Rate: 6.25 Mbps
• Supply Voltage (max): 7 V
• Supply Current: 5 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 7 V
• No. Of Channels: 8
• Uart Features: High Performance, Read/Write Burst Operation
• Supply Voltage Range: -0.5V To 7V
• Operating Temperature Range: 0°C To +70°C
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 1016-1287

xr
REV. 1.4.3
There are 8 UARTs [channel 7:0] in the 158. Each has its own 64-byte of transmit and receive FIFOs, a set of
16550 compatible control and status registers, and a baud rate generator for individual channel data rate
setting. Eight additional registers per UART were added for the EXAR enhanced features.
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 (2
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 and DLM registers) defaults to a random value upon power up. Therefore, the
BRG must be programmed during initialization to the operating data rate.
Programming the Baud Rate Generator Registers DLM and DLL provides the capability for selecting the
operating data rate.
clock at 16X clock rate. At 8X sampling rate, these data rates would double. When using a non-standard data
rate crystal or external clock, the divisor value can be calculated with the following equation(s).
4.0 UART
4.1
divisor (decimal) = (XTAL1 clock frequency / prescaler) / (serial data rate x 16),
divisor (decimal) = (XTAL1 clock frequency / prescaler / (serial data rate x 8),
Programmable Baud Rate Generator
F
IGURE
XTAL1
XTAL2
Table 9
9. B
AUD
shows the standard data rates available with a 14.7456 MHz crystal or external
Crystal
R
Buffer
Osc/
ATE
G
Channels
To Other
ENERATOR
Divide by 4
Divide by 1
Prescaler
Prescaler
27
MCR Bit-7=0
MCR Bit-7=1
(default)
16
-1) to obtain a 16X or 8X sampling clock of
Baud Rate
DLL and DLM
Generator
Registers
Logic
WITH
WITH
8XMODE [7:0]
8XMODE [7:0]
5V PCI BUS OCTAL UART
Rate Clock to
and Receiver
Transmitter
16X or 8X
Sampling
IS
IS
1
0
XR17C158