The FBM217Discrete Input Module provides 32 input channels, each accepting a 2
wire input from a dc voltage source. Associated termination assemblies (TAs) provide
for discrete inputs of under 60 Vac, 120 Vac/125 V dc or 240 Vac. The module
performs signal conversion required to interface the electrical input signals from the
field sensors to the Module Fieldbus.
Depending on the type of I/O signal required, the TAs contain current limiting devices,
high voltage attenuation circuits, optical isolation and external power source
connections.
The module with its associated TA supports the following discrete inputs:
FBM
FBM217
Inputs
30 Vdc, 125 Vdc, 120 Vac, or 240 Vac Voltage monitor or

The module can be used as a single unit, or as a redundant pair (two FBM217s).
Whenusedasaredundant pair, the modules combine to provide redundancy at the
Foxboro DCS Fieldbus Module (FBM) level, with field input signals received from one
commontermination assembly though a redundant adapter affixed to the FBMs’
baseplate. The field input current for redundant modules is doubled. A redundant
digital input block in the Foxboro DCS Control Software validates each input in
conjunction with information to/from the module, and selects the input with the highest
quality for processing in the control strategy.
In a redundant configuration, contact sense power from each module is diode OR’d
together in the redundant adapter to verify redundant power.
Aredundant contact input function block, CINR, is used for each redundant pair of
inputs. The CINR block handles input reads and initialization logic for the redundant
channels. On each execution cycle of the CINR block, identical reads are sent to both
modules, fully exercising the fieldbus and the logic circuitry of each module.
Whenconnected to the appropriate TAs, the FBM217 module provides functionality
formerly provided by the 100 Series FBM I/O subsystem. TAs are available which
support the functionality of the 100 Series main FBM07A/B, FBM08, FBM20, and
FBM24A/B/C (16 input main FBMs). Expansion TAs are available for use with these
main FBMTAsto support the functionality of expansion FBM12, FBM13, FBM21, or
FBM25A/B/C (16 input expansion FBMs)