Rockwell Automation T3419 ICS Regent Fire Detector Input - Manual (Page 3)

Fire Detector Input Modules (T3419)
P D - 6 0 3 2 M a r - 0 6
3
this regulated voltage with an internal resistor. Externally
each input connects to an associated field sensor and a line
terminator. The module monitors the input voltage to detect
a variety of input states. The module can discriminate and
report sensor tripped, sensor healthy, line open and line
shorted conditions. Additional circuits allow the module to
reset a latched fire detector by removing power from the
associated input circuit.
Internally the module generates a reference voltage that is
compared to the field inputs. The comparator generates an on
or off state depending on which voltage is greater. 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. This FPGA interfaces the input date to the
I/O safetybus and drives the module’s front panel indicators.
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.
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 modules. Discrepant data are sent through one of
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.