National Instruments PCI-232/2 Isolated 用户手册

If you are using a PCI-485 interface, you can select the transceiver 
mode for each device and select the lower baud rates listed in 

termios_program.c

 provided in your 

PCI-SERIAL

 directory. 

Use the 

rs485

 program (from the 

PCI-SERIAL

 directory) to select the 

transceiver mode. 

rs485

 sets the transceiver mode for only one serial port. 

To set the transceiver mode for other serial ports, rerun 

rs485

 with a 

different serial port number specified in the command line. For more 
information on the transceiver control modes, refer to your serial getting 
started manual. If you do not know which transceiver mode to use, choose 
Four-Wire Mode. 

Enter the following to use 

rs485

:

linux PCI-SERIAL# ./rs485 <

port number> <mode>

Enter the following to select Four-Wire Mode for 

/dev/ttyS5

:

linux PCI-SERIAL# ./rs485 5 0

To use a baud rate lower than 200, use 

setserial

 and the 

clockspeed

 

program (from the 

PCI-SERIAL

 directory) to lower the baud base of a 

single serial port from 460800 to 115200. After changing the baud base 
to 115200, the max baud rate you can achieve is 115200 baud (until you 
change the baud base back to 460800).

After you change the 

baud_base

 of the serial port using 

setserial

 and 

run the 

clockspeed

 program, you can use the lower baud rate flags in 

your programs. The 

clockspeed

 program changes the baud base of only 

Table 3.  Transceiver Mode Values

Four-Wire Mode

0

Two-Wire Mode: DTR with echo

1

Two-Wire Mode: DTR controlled

2

Two-Wire Mode: TXRDY auto 
control

3