Rockwell Automation T7404 ICS Regent+Plus AC Digital Input Module 110VAC - Manual (Page 2)

AC Digital Input Module (T7404)
2
Industrial Control Services
Module Operation
A block diagram of an AC digital input module is shown in
Figure 1.
Optical isolation between field wiring and the module’s logic
circuitry provides field-to-logic isolation — protecting the
module’s logic circuits from field signal over-voltages,
transients, and other electrical disturbances. It also provides
a safety barrier between the primary field voltages and user
accessible circuits.
Figure 1. Block Diagram of AC Digital Input Module.
When the field switch is closed, the input to the module is on.
When the field switch opens, the input to the module turns off.
Data from the logic side of the optical isolators are bused to
the I/O bus interface logic.
The processor modules send triplicated read data requests to
the input module over the I/O Safetybus. The processors’
addressing data and data read requests are voted by the