Allen-Bradley PLC-2/30 - Remote System Structure

Hardware Considerations
Chapter 2
28
on the front panel of the local adapter module aid in troubleshooting. These
indicators are:
ACTIVE — Illuminates when proper communication is established
between the processor and the I/O chassis. It also indicates that DC
power is properly supplied to the I/O chassis. It is normally on.
RACK FAULT — Illuminates when I/O data is not in the proper format.
It is normally off.
Possible causes of a rack fault are:
Data parity error on address or control lines
Missing terminator plug
Disconnected/broken communications cable
No power at the processor.
An I/O Interconnect cable is required to connect between the PLC-2/30
and local I/O rack adapter modules. It is available in two sizes:
3 ft. I/O Interconnect cable (.92m) 1777–CA
6 ft. I/O Interconnect cable (1.85m) 1777-CB
I/O Cable Terminator Plug 1777-CP
(used to “close” the I/O interconnect cable link at the last I/O adapter
module)
A remote system allows the processor and the I/O chassis to be separated
by up to 10,000 cable feet (approx. 3,048 meters). Up to 7 remote I/O
racks may be assigned.
Proper transmission of data between the PLC-2/30 processor and
remote bulletin 1771 I/O modules requires a 1772-SD2 Remote I/O
Scanner/Distribution Panel plus a 1771-ASB Remote Adapter in each I/O
chassis. Connection between the PLC-2/30 processor and the 1772-SD2
is through a 1772-CS interconnect cable. Connection from the 1772-SD2
to a 1771-ASB Remote I/O Adapter and from one remote I/O adapter to
another is through 1770-CD twinaxial interconnect cable.
The front of the 1772-SD2 distribution panel has eight bicolor red/green
LED indicators. If the I/O chassis is used and serial communication is
valid, the RACK STATUS LED will be green. If the I/O chassis is not
used, the LED is off. For an I/O rack fault condition, the corresponding
RACK STATUS LED will be red. The rack 0 indicator will also go to red
if there is a dependent I/O fault.
2.9
Remote System Structure
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