Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 122)

Publication 1785-UM012D-EN-P - July 2005
8-4 Communicating with Extended-Local I/O
• You cannot configure more than one rack to have the same starting rack
number and module group; that is, you cannot use chassis to chassis
complementary I/O.
Follow these guidelines when you plan your extended-local I/O system.
• Do not configure controller input interrupts (PIIs) for inputs in an
extended-local I/O chassis. The PII inputs must be in the
controller-resident local I/O rack.
• You can either use 32-point I/O modules and any addressing method or
use 1771-IX or -IY modules and any addressing method in extended-
local I/O racks. You must specify the type of I/O modules you are
using by setting the configuration plug on the extended-local I/O
adapter.
• If you need to use a thermocouple module and 32-point I/O modules in
the same I/O chassis, use the 1771-IXE module.
Transferring Data The PLC-5/40L or -5/60L controller can scan controller-resident I/O,
extended local I/O, and remote I/O. The following figure shows how a
PLC-5/40L or -5/60L controller accomplishes I/O scanning and update.
PLC-5/40L and -5/60L I/O Scanning and Update
Input
Output
I/O Image Table
I/O Image Table Update
Synchronous to
program scan
(during housekeeping)
Remote I/O
Buffer Update
Asynchronous to
program scan
Extended
Local
I/O
Input Output
Input
Output Input
Output
Processor-
Resident
Local I/O
Remote I/O
Link
Remote
I/O
Buffer