Rockwell Automation T8423 Trusted TMR 35 - 120 Vdc Digital Input Module - Manual (Page 11)

Trusted
TM
Module T8423
Issue 15 Apr 10 PD-T8423 11
1.4. Front Panel Unit (FPU)
The Front Panel Unit (FPU) comprises a Front Panel Termination Unit (FPTU) and a Front Panel
Display Unit (FPDU). The overall FPU contains the necessary connectors, switches, logic, and LED
indicators for the front panel. For every type of Trusted
TM I/O module, the FPU contains the Slice
Healthy, Active/Standby and Educated indicators (LEDs), and the module removal switches.
Additional bicolour LEDs provide status indication for the individual I/O signals. Serial data interfaces
connect the FPU to each of the HIU slices to control the LED status indicators and monitor the module
removal switches.
1.5. Line Monitoring Thresholds
The module determines the contact state and line fault status by comparing the input voltage level to
four user programmed thresholds and two fixed (minimum and maximum) thresholds. A “Contact
Indeterminate” region is defined between the contact Closed and Open states to account for marginal
faults in the external wiring or in the IFIU. Hysteresis is provided on the thresholds by up-scale and
downscale values, corresponding to the thresholds for increasing and decreasing values respectively.
The tables below show example threshold data for both 120Vdc input contacts and 48V dc input
contacts both with line monitoring respectively,