Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 52)

Publication 1785-UM012D-EN-P - July 2005
4-8 Addressing I/O and Controller Memory
Assigning Racks The number of racks in a chassis depends on the chassis size and the
addressing mode:
If Using this
Chassis Size 2-slot Addressing,
Results In 1-slot Addressing,
Results In 1/2-slot Addressing,
Results In
4-slot 1/4 rack 1/2 rack 1 rack
8-slot 1/2 rack 1 rack 2 racks
12-slot 3/4 rack 1-1/2 racks 3 racks
16-slot 1 rack 2 racks 4 racks
TIP
When assigning rack numbers, use the following guidelines:
• One I/O rack number is eight I/O groups, regardless of
the addressing mode that you select.
• You can assign from one to four racks in your
controller-resident local chassis (128 inputs and 128
outputs) depending on the chassis size and addressing
mode. You cannot split a controller-resident local I/O
rack over two or more chassis or assign unused
controller-resident local I/O groups to remote I/O racks.
• The default address of the controller-resident local rack is
0.
• You cannot split racks across remote I/O and
extended-local I/O links. For example, if an 8-slot
extended-local I/O chassis is configured as I/O groups
0-3 of I/O rack 2, an 8-slot remote I/O chassis cannot be
configured as I/O groups 4-7 of I/O rack 2. For more
information about addressing extended-local I/O, see
chapter 8.
• When using complementary I/O addressing, treat
complementary rack addresses individually when
grouping racks; primary rack numbers are separate from
complement rack numbers.
• If you are not using the autoconfiguration function, group
together 1/4-racks and 1/2-racks of each logical rack on
the configuration screen of your programming software.
Do not intersperse these with other rack numbers. For
example, your programming software has a screen with
the following information for defining racks:
Group together 1/4 racks
and 1/2 racks
Rack Starting Rack Range Fault Inhibit Reset Retry
Address Group Size
1 0 1/4 010-011 I 0 0
1 2 1/4 012-013 0 0 0
1 4 1/4 014-015 0 0 0
2 0 1/4 020-021 0 0 0
2 2 1/4 022-023 0 0 0
2 4 1/2 024-027 0 0 0
3 0 1/4 030-031 0 0 0
17 0 FULL 170-177 0 0 0