Remote Processing CX-10 - Manual (Page 15)

SETUP AND OPERATION - MODBUS and BASIC SECTION 2
Page 2-10
The CX-10 CPU will function down to around 3
volts. However any modbus communication may
not work and relays may not turn on. Board
operation when its internal power is below 4.5 volts.
2. Check the COM0 port (J1).
Make sure the VTC-9F serial cable is oriented
correctly. The key on the cable corresponds to a silk
screen area on the board.
Remove the connector from COM0. Refer to the
outline drawing earlier in this section. Connect an
oscilloscope (preferred) or a voltmeter to pin 3 (Txd)
and ground. Pin 3 should be -6 volts or more
negative. If you have -6 volts or more,cycle power to
the board. If you have a scope attached, you should
see a burst of activity. With a volt meter, you should
see a change in voltage. Using a Fluke 8060A set to
measure AC, you should see a momentary reading
above 2 volts.
3. Check the cable.
Install the cable and make sure the voltages and
output activity are still there. Output is from pin 3
on the VTC-9F. If not, check to make sure
something is not shorting the output. Wiring is in
SECTION 4, SERIAL PORT PIN OUT.
4. Check the serial parameters on your PC.
They should be set to:
19200 baud
No parity
8 data bits
1 stop
Make sure you have set the communications port on
your PC to the one the VTC-9F is plugged into.
5. Receiving a sign on message and can't enter
characters.
Check U10, pin 8 for at least -6 volts with the serial
cable connected to the PC. When it is near 0 volts,
the terminal or PC's Txd line is not connected. When
you press a character on the terminal or PC, you
should see the voltage go positive on the
oscilloscope.
If all of this fails, call technical support listed in
SECTION 1.