BARR/SPOOL conforms to the IBM standard for sending data to and receiving data from the PC asynchronous serial ports COM1-COM4. The following sections document the definitions for the serial port signals. The serial port can be used for driving printers or reading data from other devices.
Signals for the 25-pin serial port connector on the PC:
|
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/SPOOL 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/SPOOL. To be compatible with DOS, pin 6 should be tied to pin 5. |
|
7 |
SIG-GND |
-- |
Signal Ground. |
|
20 |
DTR |
out |
Data-Terminal-Ready. Used for flow control when receiving on a COM port. BARR/SPOOL will set this to 0 to signal the remote device to temporarily suspend data transmission. |
The terms 0 and 1 for electrical signals are used for LOW and HIGH signals.
Signals for the 9-pin serial port connector on the PC:
|
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/SPOOL 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/SPOOL. To be compatible with DOS, pin 6 should be tied to pin 8. |
|
5 |
SiG-GND |
-- |
Signal Ground. |
|
4 |
DTR |
out |
Data-Terminal-Ready. Used for flow control when receiving on a COM port. BARR/SPOOL will set this to 0 to signal the remote device to temporarily suspend data transmission. |
The terms 0 and 1 for electrical signals are used for LOW and HIGH signals.
This type of printer cable is also called a null-modem cable. It has a D25 male connector that plugs into the printer, and a D25 female connector that plugs into the PC serial port.
This type of printer cable is also called a null-modem cable. It has a D25 male connector that plugs into the printer, and a D9 female connector that plugs into the PC serial port.