Allen-Bradley PLC-2/30 - Last State Switch; I;O Rack Number

Hardware Considerations
Chapter 2
26
When using remote I/O (the 1772-SD2 scanner and the 1771-ASB remote
I/O Adapter), these switches will be set according to the adapter module’s
requirements.
The last state switch (switch no. 1) on the 1771 I/O chassis must be
properly set. ON indicates that the outputs are left in their last state when
a fault is detected. Machine operation can continue after fault detection.
OFF indicates that the outputs are de-energized when a fault is detected. In
addition, in remote systems, the switches on the 1772-SD2 Remote I/O
Scanner/Distribution panel and the 1771-ASB Remote I/O Adapter
must be properly set. Refer to publications 1772-2.18 and 1771-6.5.37,
respectively, for information on their switch settings.
WARNING: Switch No. 1 of the 1771 I/O chassis should be set
to OFF for most applications. This allows the processor to turn
controlled devices off when a fault is detected. If this switch is
set to ON, machine operation can continue after fault detection.
Damage to equipment and/or injury to personnel could result.
The setting of switches 3, 4 and 5 determines the I/O data table and
program address of the modules in this chassis — this is the local rack
number.
Improper setting of these switches will result in misdirected
communications between processor and the desired I/O rack.
2.6.1
Last State Switch
2.6.2
I/O Rack Number
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