Field Interface Unit (FIU)

The Field Interface Unit (FIU) is the section of the Module that contains the

specific circuits necessary to interface to the particular types of field I/O

signals. Each Module has three FIUs, one per slice. For the TMR 24 Vdc Digital

Input Module, the FIU contains an individual analog to digital (A/D) converter

for each of the 40 field inputs.

The FIU receives isolated power from the HIU for logic. The FIU provides

additional power conditioning for the operational voltages required by the

FIU circuitry. An isolated 6.25 Mbit/s serial link connects each FIU to one of

the HIU slices.

The FIU also measures a range of onboard “housekeeping” signals that assist

in monitoring the performance and operating conditions of the Module.

These signals include power supply voltages, current consumption, onboard

reference voltages and board temperature.