Operator Interface Module Instruction Manual

Chapter 8
Troubleshooting and Maintenance
8–12
Only available on the RS-485 version. Use the TXEN test to verify the
transmit enable line at the RS-485 communications port.
The TXEN test requires a loopback connector with an LED. You can
construct a simple loopback connector as shown below:
DB9 Female
1 Data Out –
2 Data Out +
3 Data In -
4 Data In +
5 Signal Ground
6 Transmit Enable
7 Not Used
8 Signal Ground
9 Shield
Pin Signal Name
RS-485 Port Only
Connects pins 1 !3
and pins 2 ! 4
LED and 750W resistor
between pins 2-4 and 6
Loopback Connector
750W
LED
To test the transmit enable line:
1. Use the [NEXT] and [PREV] keys to display TXEN Test on the
test selection screen.
DTAM Micro Diag Test
TXEN Test
2. Press [ ] to initiate the test.
The LED should flash at approximately 1 second intervals indicating that
the transmit enable line is functioning properly.
3. Pressing [ ] terminates the TXEN test.
The next test selection screen is displayed.
DTAM Micro Diag Test
Reset DUT
4. To terminate the test function , press the [NEXT] and [PREV] keys to
display Reset DUT in the test selection area. Press [
] to reset the
terminal.
TXEN Test