Setup 3
3 - 6
Troubleshooting:
Establishing communications is, without a doubt the most difficult process
encountered when installing an I/O PLEXER system. Every component in the
system plays a key roll in this function. The following steps should aid in the
troubleshooting an I/O PLEXER system:
Install the unit nearest to the Host computer. Connect appropriate
communications network and set the unit address and baud rate to the desired
values.
At the Host computer, run a terminal emulation program such as Windows
TM
V3.x “Terminal” (usually found in the ACCESSORIES program group) or
Windows 95 Hyper Terminal (usually found in the PROGRAMS -
ACCESSORIES menu path)
Configure the terminal program for the appropriate comm-port, baudrate, 8-data
bits, 1- stop bit, no parity, handshake = hardware or none. Set the terminal
preferences for local echo, so that the typed characters can be seen. Set the
carriage return translation (CR) to add Linefeed (CR/LF) to both the inbound and
outbound transmissions. This will scroll each line sent and received rather than
overwriting the previous for clarity.
Once the Host terminal software is configured; press the space bar and observe
the lower left bargraph segment (marked recv.) On the first I/O PLEXER chassis.
If this LED flashes each time the spacebar is pressed then assume that the
communications link to the I/O PLEXER is O.K.
If not, verify the wiring, comm port, and modem link - if any. A typical
problem here is wrong com port or incorrect wiring of the Host end of the
link.
If the Recv. LED is on constantly the RS-422/ 485 wiring is probably
backwards.
Once signal to the I/O PLEXER is verified, a valid instruction should be sent to
the unit to initiate a response. Send an “Identify station type” “F” instruction (see
appendix C,C) Be sure to send the entire instruction within 10 seconds as the I/O
PLEXER will ignore instruction that take too long to finish. If the instruction is
to a valid address for this unit and at the correct baud rate, the transmit LED
should flash immediately after the carriage return of the instruction is received
.
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