Allen-Bradley PLC-5 User Manual page 53

When assigning remote I/O rack numbers, use these
TIP
guidelines:
A single remote I/O scanner channel can support up to 32 devices
but only 16 rack numbers. For more information, see chapter 6.
Limit the number of remote I/O rack numbers to those that your
PLC-5 controller can support.
The PLC-5 controller and the 1771-ASB adapter module
automatically allocate the next higher rack number(s) to the
remaining I/O groups of the chassis. For example, if you select
1/2-slot addressing for your controller-resident local chassis and
you are using a 16-slot (1771-A4B) chassis, the controller will
address racks 0, 1, 2, and 3 in this chassis.
You can assign a remote I/O rack to a fraction of a chassis, a
single I/O chassis, or multiple I/O chassis as shown below.
I/O Rack No. 0 I/O Rack No. 1
01 23 45 67 01 23 45 67
One 16-slot chassis, two racks
0 1 2 3
One 8-slot chassis, 1/2 rack
Addressing I/O and Controller Memory
0 1 2 3
One 16-slot chassis, one rack
I/O Rack No. 3
4 5
Two 4-slot chassis, 1/4 rack each
Publication 1785-UM012D-EN-P - July 2005
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4 5 6 7
6 7
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