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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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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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

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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.

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r

AC Digital Input Module

(T7404)

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Figure 2. AC Digital Input Module.

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AC Digital Input Module

Application

Active and Fault Status Indicators

These green and red LEDs indicate the overall health of the
module. During normal operation the green ACTIVE
indicator flashes at the controller's scan rate. If a module
fault is detected the red FAULT indicator turns on and the
green indicator turns off.

Field Status Indicators

Input status indicators are located on the logic-side (after the
signal conditioning and isolation).
are lit when current is flowing through the input.

The field status indicators

Simplex Configuration

Digital input modules provide a suitable interface to non
critical input signals. Although many of the circuits in the
digital input modules are automatically tested and
annunciated, some logic circuits and all of the field-side
sensing circuits are simplex and non-tested. This simplex
input configuration is illustrated in Figure 3.

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Figure 3. Simplex Digital Input Configuration.

Fault Tolerant Connection

For critical inputs, redundant input modules are used in a
2oo3 or 1oo2 fault tolerant configuration. In these
configurations the redundant input modules are connected to
single or multiple sensors. If redundant sensors are installed

5

AC Digital Input Module

in the field, the redundant modules are connected so that each
sensor connects to one of the redundant modules. These
configurations are illustrated in Figure 4, showing triple
redundant input modules. Each AC digital input module is
hot replaceable. In triple redundant input configurations, if a
fault occurs on one module, it can be removed and replaced
while the system continues to sense the inputs from the
remaining two input modules.

(T7404)

Figure 4. Fault Tolerant Digital Input Configurations.

Field Wiring

6

For field wiring details, refer to PD-7901 - I/O Termination
Assembly.

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AC Digital Input Module

Keying

The I/O chassis can be physically keyed to prevent accidental
damage caused by inserting a module into a slot wired for a
different module type. Figure 5 illustrates how the slot keys
are installed on the I/O chassis slot field wiring connectors.
The slot key positions for the AC digital input module are
listed in Table 1.

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Mar-06

Figure 5. Installing Slot Keys.

7

Module

Upper

Connector

Lower

C

onnector

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AC Digital Input Module

(T7404)

Table 1. Slot Key Positions.

Configuration

Each input module is configured using the

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I/O
Configuration Editor. In the editor, you will perform the
three steps described below to configure the input module.

1) Set the Module Type:

Position the cursor on the module slot you wish to define.
Choose Set Module Type from the Edit Menu and select
the appropriate digital input module from the list.

2) Edit the Module Definition:

Choose Edit Module Definition from the Edit Menu. A
dialog box will open whe
definitions.

re you can define the input point

8

Figure 6. Digital Input Module Definition.

3) Edit each point:

Choose Edit from the Module Definition dialog box to
define a name and description for each I/O point. In the

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AC Digital Input Module

Digital Input Point dialog, enter a tag name (up to 12
characters) and a description (up to 40 characters).

Figure 7. Defining a Digital Input Point.

The tag names are used in the application program to
represent the input state. In addition, a module tag n

ame can
be entered to represent the combined state of all 16 inputs.
This module tag name represents the 16 inputs as a signed,
16-bit integer. In this format, input point one is the least
significant bit (LSB) and input point 16 is the most significant
bit (MSB).

Programming

Inputs are referenced in the application program through the
tag names defined in the I/O Configuration Editor. When
current flows through the input (field switch closed) the input
is said to be on, or have a value of one. In ladde

r logic, the on
state would produce power flow in a normally open (N.O.)
contact.

To program fault tolerant configurations using triplicated
digital input modules, a voter element can be used as shown
in Figure 8.

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Mar-06

Figure 8. Programming Fault Tolerant Digital Inputs.

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AC Digital Input Module

In this illustration, VOTE_A_NAME, VOTE_B_NAME, and
VOTE_C_NAME represent the three digital inputs to be two
out-of-three voted. ERROR_A_NAME, ERROR_B_NAME
and ERROR_C_NA
inputs. RESULT_NAME is the result of the voter instruction.
The field Msec is the time, in milliseconds, an input can be
incorrect before signaling an error. RESET_NAME is the
reset bit used to reset the latched error bits.

The voter instruction can be used to vote digital input points
or entire digital input modules. When voting digital input
modules, the tag names VOTE_A_NAME, VOTE_B_NAME,
and VOTE_C_NAME would be the names of the digital input
modules and RESULT_NAME would be a shared variable
register. After voting the modules, a block move instruction
should be used to move the contents of the register
RESULT_NAME into individual shared variable control
relays. Refer to the
information about the block move instruction and shared
variable definitions.

(T7404)

ME are the error bits for the digital

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INTERPRET

Help files for more

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Maintenance

No periodic maintenance or calibration is required for the AC
digital input module. There are no user replaceable parts
inside the module. In safety critical input appli
inputs should be dynamically transitioned at a period not
greater than six months.

Safety Considerations

The AC voltage digital input module is TÜV certified as non

interfering and when properly configured is also certified for
Risk Class 5 safety critical inputs. Safety critical
configurations include 2oo3 and 1oo2 voting methods.

In safety critical input applications using a single sensor, it is
important that the sensor failure modes be predictable and
well und
not responding to a critical process condition. In such a
configuration, it is important that the sensor be tested

erstood, so there is little probability of a failed sensor

cations, the

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AC Digital Input Module

regularly, either by dynamic process conditions that are
verified in the Regent, or by manual intervention testing.

Redundant sensors can be used with redundant input
modules to eliminate any single points of failure and extend
fault tolerance to include the sensors.

In all safety critical configurations and applications, the AC
voltag
trip inputs,
a period not greater than six months.

e digital input module can be used for de-energized to

only

if the inputs are dynamically transitioned at

For additional safety considerations, please refer to the Safety
Considerations section of the Regent User’s Guide.

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Safetybus Power

1.15 load units

Number of Inputs

16 circuits divided into two
groups of eight

Voltage Range

90 to 130 VAC

Frequency Range

47 to 63 Hz

Turn-On Voltage

89 VAC, minimum

Turn-Off Voltage

30 VAC, maximum

In

put Current

3.9 mA, typical

Turn-On Delay

minimum
maximum

3.5 msec
20 msec

Turn-Off Delay

minimum
maximum

3.5 msec
15 msec

Over Voltage Protection

continuous:
burst:

160 VAC
260 VAC, for 5 sec

Heat Dissipation

14 Watts, 48 BTUs/hour

Fusing

None, fuse external if
required

Isolation

2500 volts minimum (field
wiring to control logic)
2500 volts minimum (input
group 1-8 to input group
9-16)

Operating Temperature

0°

to 60° C

(32° to 140° F)

Storage Temperature

-40°

to 85° C

(-40°

to 185° F)

Operating Humidity

0 to 95% relative humidity,
non-condensing

Vibration

10 to 55 Hz:

±0.15mm

AC Digital Input Module

(T7404)

Specifications

12

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Shock

Operating:

15 g, ½ sine wave, 11 msec

Electromagnetic
Interference

•

IEC 801 Part 2 - Electrostatic
Discharges

•

IEC 801 Part 3 - Radia

ted

Electromagnetic Fields

•

ANSI/IEEE C37.90 - Surge
Withstand Capability

Level 3: Contact discharge of
6 kV
Level 3: 10 V/M, 27 MHz ­500 MHz

2.5 kV damped 1 MHz sine
wave

Safety

Certified to DIN V VDE
0801 for Risk Class 5. Also
designed to meet UL 508 and
CSA 22.2, No. 142-M1981

Dimensions

Height:
Width:
Depth:

12.6" (320 mm)

1.27" (32 mm)

10.12" (257 mm)

Weight

3.0 lbs (1.4 kg)

AC Digital Input Module

PD-7013

Mar-06

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