Bradley Smoker PLC-5 Communicating to a Remote I/O Node Adapter, Appendix E, Instructions

Communicating with Remote I/O 6-11

Communicating to a Remote I/O Node Adapter

A scanner channel exchanges discrete data with remote I/O node adapters like 1771-ASB modules via the remote I/O buffer.

Remote I/O Scan and Program Scan Loops.

Remote I/O Scan Loop Program Scan Loop

Rack 3	Adapter
Rack 2	Adapter
Rack 1	Adapter

x y

Remote I/O Buffer

Data Exchange

x y

a b

I/O Image	Update
Table	I/O image

Data

Exchange

Controller-

Resident

Rack

Housekeeping

Immediate I/O 1

IOT (x)

IIN (y)

a

write outputs

b

read inputs

Logic

Scan

The remote I/O scan is the time it takes for the controller to communicate with all of the entries in its rack scan-list once. The remote I/O scan is independent of and asynchronous to the program scan.

During housekeeping:

Data exchange between the I/O image table, the controller-resident rack, and the remote I/O buffer occurs.

The remote I/O buffer is updated.

Remember that the I/O scanner is constantly updating the remote I/O buffer asynchronously to the program scan.

1In remote racks, immediate I/O data transfers update the remote I/O buffer.

IMPORTANT

The remote I/O scan for each channel configured for scanner mode is independent and asynchronous to the remote I/O scan for any other channel

For the Scanner Channel to Communicate with the	For More Information,
1771-ASB Adapter Modules, Do the Following	See:
1.Set the I/O chassis backplane switch for each chassis that	Appendix E
houses an adapter module.
2.Set the switches on the adapter module itself.
3.Connect the remote I/O cable.	your controller installation
	instructions

Publication 1785-UM012D-EN-P - July 2005