The information in this topic documents the different wiring connections used for loopback testing. This test can best determine if the source of the issue is the serial card or connected device.
RS485 half-duplex serial cards
Figure: Wiring Connections for RS485 Half-duplex Loopback
Testing
RS422 Full-duplex serial cards
Figure: Wiring Connections for RS422 Full-duplex Loopback
Testing
Note
Port 1 does not need to be the master. Port 2 can be the master as long as Port 1 is the slave.
RS232 serial cards
Figure: Wiring Connections for RS232 Loopback Testing
Figure: Wiring Connections for RS232 (DTR & DSR not used) Loopback
Testing
Note
Port 1 does not need to be the master. Port 2 can be the master as long as Port 1 is the slave.