Communicating with Remote I/O 6-3

 

 

Introduction to Remote I/O

A remote I/O system lets you control I/O that is not within the controller’s

 

chassis. A PLC-5 controller channel, in scanner mode, transfers discrete and

 

block-transfer data with remote I/O devices.

 

An example remote I/O system looks like this:

A PLC-5 controller channel acting as a scanner

The scanner channel maintains a list of all the full and partial racks connected to that channel, which is

the scan list.

Remote I/O link cable: Belden 9463

Remote I/O node adapters like the 1771-ASB modules or PanelView operator interfaces addressed

as remote I/O racks.

PLC-5 channel or a controller operating as a remote I/O adapter

PLC-5/40

1771-ASB

PLC-5/20

The remote I/O scanner channel keeps a list of all of the devices connected to each remote I/O link called a scan list. An example channel scan list looks like this:

PLC-5/40E

Ch 1A

Ch 1B

Rack 1

Rack 2

Rack 3

Ch 1B Scan List

Rack

Starting

Rack

Range

Address

Group

Size

 

1

0

Full

010-017

2

0

1/2

020-023

3

0

Full

030-037

 

 

 

 

 

 

 

 

In this example, channel 1B continually scans the three racks in its scan list and places the data in the remote I/O buffer in the controller. The controller updates its own buffer and the I/O image table. During housekeeping, the two buffers are updated by exchanging the input and output data with each other.

For more information on scan lists, see page 6-9.

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Publication 1785-UM012D-EN-P - July 2005

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Bradley Smoker PLC-5 user manual Introduction to Remote I/O, Block-transfer data with remote I/O devices