4101-2 Controller Installation Handbook
8-8
Expanded system - at least three Comms modules
Computer
4232 (addrs 0)
Controller
d/s 485
4230 C/M
u/s
232
u/s 485
d/s 485
Controller Controller Controller
4232 (addrs 1)
Controller
d/s 485
Controller Controller Controller
u/s
485
d/s
485
An expanded system with three Comms modules gives two branches
of Controllers. The first Comms module is a 4230 (or 4235 for a large
system) set to address F and communicates with the computer
upstream and all the 4232 Comms modules in parallel downstream
(up to a maximum of 10 - addresses 0 to 9). Each 4232 Comms
module communicates with a branch of Controllers downstream (up
to a maximum of 32 Controllers per branch) and with the 4230
Comms module upstream. This layout polls all the Controllers in
both branches at equal rates.
Extending the length of a branch
If the overall length of cable in a branch of Controllers exceeds the
limit for RS485 (1km) then a 4232 Comms module set to address E
can be used half way as a “repeater” to extend the length of the
branch.
Computer
4230 C/M
Controller
up to 1km
u/s
RS232
d/s
RS485
Controller Controller
4232 (type E)
Controller
u/s
RS485
d/s
RS485
up to 1km
When the 4232 Comms module is set to type E, it passes on the
messages it receives in either direction without adding any address of
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