Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 68)

Publication 1785-UM012D-EN-P - July 2005
4-24 Addressing I/O and Controller Memory
Effectively Using
I/O Memory The PLC-5 controller automatically allocates both an input and output
memory location to each I/O location. I/O modules generally only use either
the inputs or the outputs. To more effectively use I/O memory, you can use
these methods of placing I/O modules.
Use Application
2-slot Install 16-point I/O modules as an input module and output module pair in
an I/O group. For example, if you place an input module in slot 0, place an
output module in slot 1.
1-slot Install 32-point I/O modules as an input module and an output module
pair in an I/O group. For example, if you place an input module in slot 0,
place an output module in slot 1.
complementary I/O chassis You configure complementary chassis with a primary and complement
chassis pair. You complement the I/O modules I/O group for I/O group
between the two chassis. The I/O modules in the complementary chassis
perform the opposite function of the corresponding modules in the
primary chassis.
By designating a PLC-5 scanner channel as complementary, you can
complement racks 1-7. A channel configured for complementary I/O can’t
scan racks greater than 7. Those PLC-5 controllers that can address rack
numbers greater than 7 can address these racks on another scanner
channel which has not been configured as complementary. The remote
I/O link device (such as a1771-ASB adapter) must also be configured for
complimentary.
For more information see the PLC-5 Reference Guide: Configuring
Complementary I/O for PLC-5 Controllers, publication 1785-6.8.3.