Rockwell Automation T8451 Trusted TMR 24V dc Digital Output Module - 40 Channel - Manual (Page 9)

Trusted
TM
Module T8451
Issue 12 Apr 10 PD-T8451 9
Fig 2 shows a simplified block diagram of the Trusted TM 24V dc Digital Output 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 all three FIUs to a
single field interface. The FTU provides the Group Fail-safe switches and passive components
necessary for signal conditioning, over-voltage protection, and EMI/RFI filtering. When installed in a
Trusted
TM Controller or Expander Chassis, the FTU field connector interconnects to the Field 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 field connector 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 TMR 24V dc Digital Output Module, the FIU contains one stage of the output switch structure, and
sigma-delta (JK) output circuit for each of the 40 field outputs. Two additional JK circuits provide
optional monitoring of the external field I/O supply voltage.
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 6.25Mbit/sec 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