Bradley Smoker PLC-5 user manual Discrete Data Transfer, Remote I/O Scan, Logic Scan

Communicating with Extended-Local I/O 8-5

Discrete Data Transfer

The processors scan the extended-local I/O chassis during the housekeeping portion of the program scan. Extended-local I/O discrete data is exchanged between the processor’s data table image and the I/O in the extended-local I/O chassis.

Rack 3

Rack 2

Rack 1

Adapter AdapterAdapter

x y

Data

Exchange

Remote I/O

Buffer

a b x y

Remote I/O

Scan

Extended

-local I/O

Data

Exchange

I/O Image
Table		Update
		I/O image
	Data
	Exchange

Processor-

Resident

Rack

a

write outputs

b

read inputs

Immediate I/O 1

IOT (x)

IIN (y)

Housekeeping

Logic

Scan

Program Scan

Data exchange occurs during housekeeping. Outputs are written to and inputs read from the I/O image table during the logic scan.

1IIN and IOT data transfer directly to and from I/O modules extended-local I/O chassis.

The time that it takes to scan extended-local I/O chassis is added to the housekeeping time as shown in the following figure.

PLC-5/40L and -5/60L Extended-Local I/O Scan Time

						Logic Scan
Processor	Remote	Processor	+	Extended-
	I/O Buffer	Resident		Local I/O	Housekeeping
Checks
	Update	I/O Update		Scan

Program Scan

Publication 1785-UM012D-EN-P - July 2005