4101-2 Controller Installation Handbook
8-18
Notes about installing Comms modules
1. The maximum cable length for RS232 is 15m which means
that the cable from the computer to the Comms module must
not be longer than this. If this distance must be greater than
15m then use an RS232 to RS485 converter at the computer
end and connect to the upstream RS485 connections of the
Comms module.
2. The maximum cable length for RS485 is 1km. If it is necessary
for the cable in a branch to be longer than 1km then you can
use a “repeater” 4232 Comms module set to type E.
3. All devices connected to an RS485 branch must be set to the
same baud rate. Controllers are fixed to 9600 baud so any
branch with Controllers must operate at 9600 baud. A branch
containing only Comms modules can be set to any baud rate.
4. You must not plug more than two Comms modules into any
one Controller.
LEDs
Upstream
Rx
LED
Upstream
Tx
LED
Downstream
Rx
LED
Downstream
Tx
LED
Power up (Comms modules with DIR/DIAL link set to DIR)
When a Comms module is powered up, all four LEDs flash on and off
together a number of times depending on the type of Comms module,
each flash lasting 1 second: three flashes on a 4230, four flashes on
a 4235 and five flashes on a 4232.
After the flashing sequence, the downstream Tx LED (the left LED of
the right hand pair, D6) flashes very quickly 110 times as the Comms
module polls all possible downstream Controller and Comms module
addresses (20 times if JU3 is set to B). Whenever it receives a
response from an address, the Rx LED flashes (D5) and the Comms
module adds that address to its Polling List. If you watch the LEDs
during this process and see that the Rx LED does not flash even once
then the Comms module has failed to detect anything downstream
and you may have a wiring problem. If the Comms module detects a
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