Rockwell Automation T3418F User Manual

ICS Regent
®
PD-6027
Monitored Digital Input Modules, Field
Powered (Type F)
24 to 48 VDC, 120 VAC/DC
(T3411F, T3418F)
Issue 1,
Monitored digital input modules provide input sensing for 16 field input devices. The field powered (Type F) modules are suitable for inputs that are directly powered from an external field power supply. Two types of modules are available for inputs powered from 24 to 48 VDC and 120 VAC/DC. With a line monitor device installed at the field switch, monitored digital input modules detect input switch status and field wiring open and short circuits (VDC powered inputs only). Input and line status are reported back to the controller for use in application program logic.
March, 06
Features
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The input module circuits are completely and automatically tested, providing a f
Sixteen input points, powered from external field supply. Fault tolerant operation when connected in parallel with
another module of the same type. Hot-replaceable. Complete, automatic testing of all input circuits. Automat
faults. Individual front panel indicators on each module show the
module’s active/fault and power status, as well as input status and line fault status for each point.
2500 volt minimum electrical isolation between field and logic circuits.
TÜV certified, Risk Class 5.
1
ic line monitoring detects open and short field wiring
ail-safe interface for safety-critical inputs.
Monitored Digital Input Modules
Two or three monitored digital input modules can be connected in parallel to obtain fault tolerant input sensing. In these fault tolerant configurations, a failed module can be removed and replaced without interrupting the input signals.
The module requires connection to the same field power supply that powers the field switches. This field power is internally regulated by the module to power the module’s input interface circuits.
, T
ype F (T3411F, T3418F)

Module Operation

A block shown in Figure 1.
diagram of a typical monitored digital input module is
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Figure 1. Block Diagram of the Type F, Monitored Digital Input Modules.
An external field power supply provides power directly to field switches. This power supply is also connected to the
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Monitored Digital Input Modules
Important:
monitored input module. The field power is internally regulated to power the input module’s field interface circuits. The switched side of each input is wired bac module terminal screws. Inside the input module the signal passes through an internal dropping resistor and back to the field power supply return. Optionally a line monitor device can be connected across the input switch in the field (as shown in Figure 1).
Line monitoring only applies to inputs powered by a well regulated (± 5%) DC voltage power supply. Line monitoring is not supported for inputs powered from 120 VAC power sources.
The input module monitors the voltage of the input circuit at the internal dropping resistor, comparing it to a reference voltage generated by the D/A converter inside the module. The T3418F input module rectifies the input signal for 120 VAC applications. The comparator generates an on or off state depending on which voltage signal is greater than the other.
, Type F (T3411F, T3418F)
k to the input
The field-side FPGA controls and monitors the reference voltage signal and reads the status of all 16 input comparators. This information is stored and sent thro optical isolation to the logic-side FPGA. The logic-side FPGA interfaces the input data to the I/O Safetybus and drives the module’s front panel status LEDs.

Testing and Diagnostics

Standard I/O Module Testing

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 module (preventing I/O Safetybus failures upstream from the module from affecting its ability to be read). The voted r 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 the three bus drivers is independently controlled — preventing failures in a single driver from being propagated into the rest of the system.
ugh
esult
PD-6027
Mar-06
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Monitored Digital Input Modules
The bus drivers then move the data onto the I/O Safetybus which, in turn, passes it to the processors.
Each module’s voter circuits are periodically tested by the processor mod three legs of the I/O Safetybus to determine whether the 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 address that module and its points specifically. The processor modules periodically check each module’s identification code to determine whether the type of module installed matches type of module indicated in the I/O configuration that was loaded when the system was started. If a module is removed, or is replaced with a module of a different type, the processor modules will indicate I/O module errors.
, T
ype F (T3411F, T3418F)
ules. Discrepant data are sent through one of
chassis slot and
Loopback logic tests periodically write data to the module and then read it back to d interface logic is functioning correctly.

Input Circuit Testing

etermine whether the module’s I/O bus
The field interface circuits of the monitored input module are completely tested to detect stuck-on or stuck-off input circuit faults and optionally identify input wiring open and short circuits. The automatic execution and evaluation of the input testing is controlled by the triplicated Regent processor modules.
During normal operations, the internal reference voltage is set to three levels and the comparator output is read. These three reference voltage levels represent thresholds that determine whether the input signal is on or off and if the field wiring is open circuit or short circuit. The logic-side FPGA determines input status and line fault status based on the comparator data for the three voltage levels. The FPGA data is provided to the I/O processors for application processing.
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On a background basis, the I/O processors test the input circuit comparators and logic circuits for stuck-on and s
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tuck
-
Monitored Digital Input Modules
Note:
off failure modes. During testing the D/A converter generates two reference voltages outside the normal operating range of the field input voltages to test that the comparator output can turn-off and turn-on. The I/O processors read the resulting input status, line fault status, and reference voltage readings for the test cycle to determine if there are faults in the input circuits or the common data paths.
If the I/O processors detect a faulted input circuit, an I/O module fault is indicated at the Fault LED on the face of the input module is turned on.
, Type F (T3411F, T3418F)
processor modules and the

Input Circuit Test Interval

The Regent processor modules schedule testing of the input circuits on a background basis. The test interval for these circuits may range from a few seconds to several minutes, depending on the application program scan time and the size of the I/O configuration. The equation below can be used to estimate the test interval for monitored digital inputs.
TI = 172 * IOU
where:
TI
IOU
TSCAN
=
=
QTY
=
* TSCAN + 2
QTY
Test interval, seconds Quantity of I/O Units in the system (1 to 16) The application program scan time, seconds
For example, for a system with 8 I/O units and an application scan time of 60 milliseconds, the test interval would be:
TI = 172 * IOU TI = 84.6 seconds
* TSCAN + 2 = 172 * 8 * 0.060 + 2
QTY
In this system, all of the monitored input modules would be tested for stuck-on and stuck-off faults approximately every 85 seconds. This test interval can be used in reliabil
ity and availability calculations to select the fault tolerant input configuration that meet the application’s safety requirements.
PD-6027
Mar-06
Due to I/O processor fault filtering algorithms, it may take up to four test intervals to report a failed input module as a permanent fault
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Monitored Digital Input Modules
, T
ype F (T3411F, T3418F)

Front Panel Indicators

Figure 2 shows the physical features of the type F, monitored digital input modules. The front panel of each module contains fault/active and power indicators for the module well as input status indicators for each channel.

Active/Fault Status Indicator

as
This green and red LED pair indicates the overall health of the module and its field circuits. During normal operation the green ACTIVE indicator flashes at the controller's scan rate. If a module fault occurs the red FAULT indicator turns on and the green indicator turns off.

Power Status Indicator

The POWER GOOD LED indicates the presence of field voltage at the module’s field power input terminals and the overall health of the module’s field power regulator circuits.

Input Status Indicators

Input status indicators show contact and line status for each point.
A yellow contact status indicator is turned on when the contact is closed or the line has shorted.
A red line status indicator is turned on when the field wiring is open circuit or short circuit. If line monitoring is not desired, this LED can be disabled (see Disable Fault LED, page 21 for more details).
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Monitored Digital Input Modules
, Type F (T3411F, T3418F)
PD-6027
Mar-06
Figure 2. Type F, Monitored Digital Input Modules.
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Monitored Digital Input Modules
, T
ype F (T3411F, T3418F)

Application

Simplex Configuration

Monitored digital input modules provide a suitable interface to safety-critical input signals. The circuits in the monitored digital input modules are automatically tested and annunciated, providing a fail-safe interface to digital inputs. This simplex input configuration is illustrated in Figure 3.
Figure 3.

Fault Tolerant Configurations

For fault tolerant applications, redundant monitored input modules are used in a fault tolerant configuration. In one configuration the redundant input modules are connected in parallel to a single field input device as illustrated in Figure 4
. If redundant field sensors are installed in the field, the modules are connected so that each sensor connects to one of the modules as illustrated in Figure 5. In these fault tolerant configurations, each monitored digital input module is hot replaceable. If a fault occurs on one module, it can be removed and replaced while the system continues to correctly sense the inputs from the remaining module(s).
Single Monitored Digital Input Configuration.
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Monitored Digital Input Modules
, Type F (T3411F, T3418F)
Figure 4. Fault Tolerant Monitored Digital Input Modules
Connected to a Single Sensor.
PD-6027
Mar-06
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