Rockwell Automation T8402 Trusted Dual 24V dc Digital Input Module - 60 Channel - Manual (Page 9)

Trusted
TM
Module T8402
Issue 13 April 10 PD-T8402 9
Figure 2 shows a simplified functional block diagram of the Trusted TM Dual 24V dc Digital Input
Module.
Figure 2 Functional Block Diagram
1.1. Field Termination Unit (FTU)
The Field Termination Unit (FTU) is the section of the I/O module that connects the appropriate two
FIUs to a single field device as shown in Figure 1. The FTU primarily contains passive components
(scaling resistors) necessary for front-end signal conditioning, field signal over-voltage protection, and
EMI/RFI filtering. When installed in a Trusted
TM Controller or Expander Chassis, the FTU field
connector interconnects to the I/O cable assembly attached at the rear of the chassis.
The SmartSlot link is passed from the HIU to the field connections via the FTU. These signals go
directly to the I/O cable assembly and maintain isolation from the I/O signals on the FTU. The
SmartSlot link is the intelligent connection between active and standby modules for co-ordination
during module replacement.
1.2. 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 Dual 24V dc Digital Input module, the FIU contains an individual analogue to digital (A/D) converter
for each of the 60 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 serial link connects
each FIU to one of the HIU slices.
The FIU also measures a range of on-board “house-keeping” signals that assist in monitoring the
performance and operating conditions of the module. These signals include power supply voltages,
current consumption, on-board reference voltages, board temperature, and condensation.