User manual

Publication 1768-UM001C-EN-P - November 2007

62 Configure and Monitor I/O

Determine When Data

is Updated

CompactLogix controllers update data asynchronously with the execution of

logic. Use the flowchart to determine when a producer, such as a controller,

input module, or bridge module, will send data.

Overview - Updating Data

Input or output data?

Input

Output

Local or distributed?

Distributed

Local

Data is read from the module at the

configured RPI.

Local or distributed?

Distributed

Over an EtherNet/IP network, distributed

data is usually sent close to the RPI.

Data is written to the module at the RPI

and at the end of every task.

IMPORTANT

If you need I/O values used during logic execution to be from

one moment in time, such as at the beginning of a ladder

program, use the Synchronous Copy (CPS) instruction to buffer

I/O data.