Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual - Manual (Page 18)

Understanding Your System
Chapter 1
1-8
Use scanner mode whenever you want a Classic PLC-5 processor to scan
and control remote I/O link(s). The scanner-mode processor also acts as a
supervisory processor for other processors that are in adapter mode.
The scanner-mode processor scans the processor memory file to read
inputs and control outputs. The scanner-mode processor transfers
discrete-transfer data and block-transfer data to/from the processor-resident
local rack as well as to/from modules in remote I/O racks.
A PLC-5 processor scans processor-resident local I/O synchronously to the
program scan. A PLC-5 processor scans remote I/O asynchronously to the
program scan, but the processor updates the input/output image data table
from the remote I/O buffer(s) synchronously to the program scan. This
occurs at the end of each program scan.
Remote I/O
Link
Remote I/O
Scan
ProcessorĆResident
Synchronous to
Program Scan
Asynchronous to
Program Scan
Output Input
Input
Output
Remote
I/O
Buffer
Input
Output
ProcessorĆ
Resident
I/O
ScannerĆMode
PLCĆ5
Processor
Local I/O Scan
The scanner-mode PLC-5 processor can also:
gather data from node adapter devices in remote I/O racks
process I/O data from 8-, 16-, or 32-point I/O modules
address I/O in 2-, 1-, or 1/2-slot I/O groups
support a complementary I/O configuration
support block transfer in any I/O chassis
Configure the PLC-5/15 or -5/25 processor for scanner mode by setting
switch assembly SW1.
Using the Classic PLCĆ5
Processor as a Remote I/O
Scanner