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Auxiliary I/O Board
3
FUNCTIONAL THEORY OF OPERATION
The following theory of operation describes the operation of the Auxiliary I/O Board circuitry at a functional lev-
el. The information is presented to give the service technician a basic understanding of the functions performed
by the module in order to facilitate maintenance and troubleshooting to the module level. Refer to Figure 3 for a
block diagram of the Auxiliary I/O Board.
Functional Overview
4
Introduction
The Auxiliary I/O Board serves as the interface between the customer aux-
iliary equipment and the Station Control Module (SCM). In general, the
Auxiliary I/O Board routes parallel input and output auxiliary equipment
control signals between the SCM and the auxiliary equipment. There are
23 inputs and outputs available on the Auxiliary I/O Board, for connec-
tion with external equipment at any one time. There are 11 inputs and 12
outputs.
The SCM host processor reads and writes the auxiliary information with
16 bit data telegrams via the Serial Peripheral Interface (SPI). The hard-
ware functionality of the Auxiliary I/O Board (e.g., Ext_Failsoft, Rx_Lock
and Ext_Alarms) is determined by the SCM software.
As shown in the block diagrams in Figures 3, the Auxiliary I/O Board con-
tains signal buffer and latch circuits. Also provided are jumper fields
which are used for various system configuration requirements.
68P81096E53-C
09/30/05
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