DNF Controls Analyst, RS422/RS232 Tester - Manual (Page 22)

Externally Powered and Port Powered Adapters
PORT POWERED ADAPTER
Port powered adapters typically have their RS232 ports configured as DCE ports, so
they will plug into the DTE port on a computer. Power is drawn from the RTS and DTR
signal lines on the RS232 port. If the adapter’s RS232 port is configured as a DTE port,
it will not be able to draw power from the computer and will not operate.
The Analyst’s OUT RS232 port is configured as a DTE port, like on the computer. The
OUT port supplies power (up to 20ma. total) on the RTS and DTR lines to power the
adapter. The IN RS232 port is configured as a DCE port. The IN port supplies power
(up to 20ma. total) on the CTS and DSR lines to power the adapter.
If a port powered adapter is connected to an RS232 port with the incorrect configuration,
it will not receive power from the port and will not operate.
Troubleshooting Tip
If the port powered adapter does not work when connected to the OUT RS232 port,
move it to the IN RS232 port and repeat the test process.
If the port powered adapter does not work when connected to the IN RS232 port, move
it to the OUT RS232 port and repeat the test process.
If the adapter does not work on the IN or OUT RS232 port, it may be faulty.
EXTERNALLY POWERED ADAPTER
Externally powered adapters use an external power supply to operate and do NOT
require power from the RS232 port. The RTS and DTR signal lines are used only for
hardware handshaking.
If an externally powered adapter is connected to an Analyst RS232 port with the
incorrect configuration, press the appropriate [RxTx] key to swap the port transmit and
receive lines. The adapter should begin to operate properly.
Troubleshooting Tip
If the externally powered adapter works in the RS422 transmit to RS232 receive
direction but not in the other direction, change the RS232 ports between the IN port and
OUT. It should now work in both directions. The reason is that some adapters use the
RTS handshaking signal line to control the adapter’s RS422 transmitter. If the adapter is
connected to the wrong port configuration, the RTS line will not be driven properly,
thereby turning off the RS422 transmitter.
Page 18 of 31 The Analyst RS422/RS232 Tester