Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 32)

Publication 1785-UM012D-EN-P - July 2005
1-14 Understanding Your Programmable Controller
Using a PLC-5/40L, -5/60L
Programmable Controller
as an Extended-Local I/O
Scanner Use the extended-local I/O link when you need I/O updates more quickly
than is possible from remote I/O link. An extended-local I/O link provides
faster scan and update time than a remote I/O link. The extended-local I/O
link is limited to 30.5 cable-m (100 cable-ft). If an I/O chassis is located more
than 30.5m from the controller, you must use a remote I/O link.
PLC-5/60L
1771-ALX
Extended-local
I/O Link Cable:
1771-CXx
The extended-local I/O link is a parallel link that enables a
PLC-5/40L or -5/60L controller to scan a maximum of 16
extended-local I/O chassis.
A PLC-5/40L or -5/60L controller (channel 2) and an
extended-local I/O adapter module (1771-ALX) form an
extended-local I/O link.
Due to the cabling design, you can remove an adapter module
from a chassis on the extended-local I/O link without disrupting
communication to other chassis on the extended-local I/O link.
Important: The PLC-5/40L and -5/60L controllers cannot be
used as extended-local I/O adapters.
Remote I/O
Link
Output Input
Remote
I/O
Buffer
Input
Output
Controller-
Resident
Local I/O Extended-
Local
I/O Link Input
Output
PLC-5 data table
PLC-5 data table
is updated
synchronously to
program scan
(at housekeeping).
Remote I/O buffers
are updated
asynchronously to
the program scan.
Output Input