BARR/3270 conforms to the IBM standard for sending and receiving data to serial ports COM1 and COM2. The following table documents the definitions for the serial port signals.
|
Pin Number |
Name |
Direction |
Description |
|
1 |
PRO-GND |
-- |
Protective Chassis Ground. |
|
2 |
TXD |
out |
Transmit Data. |
|
3 |
RXD |
in |
Receive Data. Used for XON/XOFF flow control and receive data. |
|
4 |
RTS |
out |
Request-To-Send. Always set by BARR/3270 to 1. |
|
5 |
CTS |
in |
Clear-To-Send. Used for flow control. If CTS=0 then no data will be sent. This line can be jumpered to RTS to force CTS=1. |
|
6 |
DSR |
in |
Data-Set-Ready. Used for flow control by DOS. May be used for flow control by BARR/3270. To be compatible with DOS, pin 6 should be tied to pin 5. |
|
7 |
SIG-GND |
-- |
Signal Ground. |
|
20 |
DTR |
out |
Data-Terminal-Ready. BARR/3270 sets this line to 1 only if data can be received on RXD. It is set to 0 when BARR/3270 has more than 2000 characters of data read from the serial port buffered in memory. |
The terms 0 and 1 for electrical signals are used for LOW and HIGH signals.
|
Pin Number |
Name |
Direction |
Description |
|
3 |
TXD |
out |
Transmit Data. |
|
2 |
RXD |
in |
Receive Data. Used for XON/XOFF flow control and receive data. |
|
7 |
RTS |
out |
Request-To-Send. Always set by BARR/3270 to 1. |
|
8 |
CTS |
in |
Clear-To-Send. Used for flow control. If CTS=0 then no data will be sent. This line can be jumpered to RTS to force CTS=1. |
|
6 |
DSR |
in |
Data-Set-Ready. Used for flow control by DOS. May be used for flow control by BARR/3270. To be compatible with DOS, pin 6 should be tied to pin 5. |
|
5 |
SIG-GND |
-- |
Signal Ground. |
|
4 |
DTR |
out |
Data-Terminal-Ready. BARR/3270 sets this line to 1 only if data can be received on RXD. It is set to 0 when BARR/3270 has more than 2000 characters of data read from the serial port buffered in memory. |
The terms 0 and 1 for electrical signals are used for LOW and HIGH signals.
This type of printer cable can be called a null-modem cable.
|
Printer |
|
PC
COM1, COM2 |
|
PRO-GND 1 |
▬▬▬▬▬ |
PRO-GND 1 |
|
RXD 3 |
◄▬▬▬▬ |
TXD 2 |
|
TXD 2 |
▬▬▬▬► |
RXD 3 |
|
SIG-GND 7 |
▬▬▬▬▬ |
SIG-GND 7 |
|
DTR 20 |
▬▬▬▬► |
CTS 5, DSR 6, and DCD 8 |
|
CTS 5, DSR 6, and DCD 8 |
◄▬▬▬▬ |
DTR 20 |
This type of printer cable can be called a null-modem cable.
|
Printer |
|
PC
AT COM1, COM2 |
|
RXD 3 |
◄▬▬▬▬ |
TXD 3 |
|
TXD 2 |
▬▬▬▬► |
RXD 2 |
|
SIG-GND 7 |
▬▬▬▬▬ |
SIG-GND 5 |
|
DTR 20 |
▬▬▬▬► |
CTS 8, DSR 6, and DCD 1 |
|
CTS 5, DSR 6, and DCD 8 |
◄▬▬▬▬ |
DTR 4 |