Rockwell Automation T3418F ICS Regent Monitored Digital Input Modules, Field Powered (Type F) - Manual (Page 3)

Monitored Digital Input Modules, Type F (T3411F, T3418F)
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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 back to the input
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.
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 through
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 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 the three bus drivers is independently
controlled — preventing failures in a single driver from being
propagated into the rest of the system.
Important: