Rockwell Automation T7404 User Manual

ICS Regent+ Plus

®

PD-7013

AC Digital Input Module

110 VAC

(T7404)

Issue 1,

The AC digital input module provides input sensing for 16
field input switches. One type of module is available for
interfacing to inputs powered from 110 VAC field power
su

pplies. The module's triplicated I/O Safetybus interface
ensures that no failure in the module can affect the operation
of the Regent system or other I/O modules in the system.
Extensive fault detection and annunciation of critical
redundant circuits help prevent the controllers from receiving
erroneous data from a faulty input module.

March, 06

Features

·

Sixteen input circuits, configured as two isolated groups of
eight circuits each.

·

Fault toleran
redundant modules of the same type.

·

Hot-replaceable.

·

Automatic self-testing of triplicated I/O Safetybus circuits and
many simplex logic circuits.

·

Individual front panel indicators on each module show active
and fault status and logic-side input on/off status.

·

2500 volt minimum electrical isolation between field and logic
circuits.

·

TÜV certified, Risk Class 5.

Three AC digital input modules can be connected in parallel
to obtain fault tolerant input sensing. In this triple module
configuration, a failed module can be removed and replaced
without interrupting the input signals.

t operation when connected in parallel with

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1

AC Digital Input Module

(T7404)

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 —
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.

prote

cting the

2

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

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(T7404)

module (preventing I/O Safetybus failures upstream from the
module from affecting its ability to be read). The voted result
is then passed to the I/O bus interface logic.

After receiving the voted data read request, the I/O bus
interface logic sends its input data to the module’s three bus
drivers. Each of t
powered and controlled by the I/O transceiver modules—
preventing failures in a single driver from propagating to the
other two busses.

The bus drivers transmit the data across the backplane I/O
Safetybus to the I/O transceivers which, in turn, transmit the
data to the processors.

he three bus drivers is independently

AC Digital Input Module

Testing and Diagnostics

Each module’s voter circuits are periodically tested by the
processor modules. Discrepant data are sent through one of
three legs of the I/O Safetybus to determine whe
module’s voter is able to outvote the incorrect data. A failure
to return the correct majority-voted result to the processors
produces an I/O module error indication at the processor
modules and a module fault indication at the I/O module.

Each type of module has a unique identification code that is
read by the controller. This code lets the controller know
which type of module is installed in each I/O chassis slot and
how to address that module and its points specifically. If a
module is removed, or is replaced with a module of a different
type, the processor modules will indicate I/O module errors.

Loopback logic tests periodically write data to the module and
then read it back to determine whether the module’s I/O bus
interface logic is functioning correctly.

Front Panel Indicators

ther the

PD-7013

Mar-06

Figure 2 shows the physical features of the AC digital input
module. The front panel of each module contains active and
fault status indicators and field signal status indicators fo
each circuit.

3

r

AC Digital Input Module

(T7404)

4

Figure 2. AC Digital Input Module.

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