Chapter 2
Description
Rockwell Automation Publication ICSTT-RM451D-EN-P - March 2021
11
Figure 2 shows a simplified block diagram of the Trusted 24/48V DC Digital
Output Module.
Figure 2: Functional Block Diagram
The Field Termination Unit (FTU) is the section of the I/O Module that
connects all three FIUs to a field interface. The FTU provides the Group Fail-
Safe switches and passive components necessary for signal conditioning,
overvoltage protection, and EMI/RFI filtering. When installed in a Trusted
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 coordination during
Module replacement.
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/48V
DC Digital Output Module, the FIU contains one stage of the output switch
structure, and sigma-delta (
Σ
Δ) output circuit for each of the 40 field outputs.
Two additional
Σ
Δ circuits provide optional monitoring of the external field
I/O supply voltage.
Field Termination Unit (FTU)
Field Interface Unit (FIU)
