DESCRIPTION
LOGIC POWER
2 - 4
WBPEEUI240752A0
®
LOGIC POWER
Logic power (+5 VDC) drives the DSI circuits. It connects
through the top 12-pin card edge connector (P1) show in
Figure
I/O EXPANDER BUS
The INFI 90 OPEN I/O expander bus is a high speed synchro-
nous parallel bus. It provides a communication path between
control modules and I/O modules. The control module pro-
vides the control functions and the DSI module provides input
to the control module. The P2 card edge connector of the DSI
and control module connect to the bus.
The I/O expander bus is parallel signal lines located on the
module mounting unit (MMU) back plane. A 12-position dip-
shunt placed in a connection socket on the MMU back plane
connects the bus between the control and I/O modules. Cable
assemblies can extend the bus to six MMUs.
A control module and its I/O modules form an individual sub-
system within a process control unit (PCU). The I/O expander
bus between control and I/O module subsystems must be sep-
arated. Leaving a dipshunt socket empty or not connecting the
MMUs with cables separates them.
UNIVERSAL I/O EXPANDER BUS INTERFACE
The DSI uses a custom gate array to perform the I/O expander
bus interface function. All the control logic and communica-
tion protocol are built into an integrated circuit (IC). This IC
provides the following functions:
•
Address comparison and detection.
•
Function code latching and decoding.
•
Read strobe generation.
•
Data line filtering of bus signals.
•
On-board bus drivers.
