User`s guide

Page 17

Controlinc 1746-C (Version 5.21) Network Master Users Guide (2004-11-18)

4.1.2. Diagram Describing Network Scanning & Actuator Writing Logic

This example demonstrates how a normal scan cycle gets elongated with data writes to the actuators.

The more writes being performed the longer it will take to complete data scans. This is where the

PLC/HMI must make a value decision for the best fit for their application:

• Fast enough repetitive writes to control the system

• Slow enough repetitive to ensure effective feedback to control the system.

Time to poll 30

actuators for

data … without

any writing to

actuators

Time to poll 25

actuators for data …

Performing 3 sets of

data writes

interspaced within

the single scan loop

Polling

for data

Writing

data

Polling

for data

Writing

data

Writing

data

Polling

for data

Polling

for data

Polling data …

“Network Scan

Time-Slice”

Writing data to

the network …

“PLC Interface

Time-Slice”