DESCRIPTION AND OPERATION
OUTPUT CIRCUIT CONNECTIONS
WBPEEUI240754A0
2 - 3
OUTPUT CIRCUIT CONNECTIONS
The output signals connect to the 30-pin card edge connector
P3 of the DSO using a termination cable from a termination
unit (TU) or a termination module (TM). Proper polarity wiring
of field signals is necessary for the output circuits to function
properly.
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 I/O module provides the
input/output functions. The P2 card edge connector of the I/O
module and control module connect to the bus.
The I/O expander bus is parallel signal lines located on the
module mounting unit (MMU) backplane. A 12-position dip-
shunt placed in a connection socket on the MMU backplane
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 subsystems must be separated.
Leaving a dipshunt socket empty or not connecting the MMUs
with cables separates them.
UNIVERSAL I/O EXPANDER BUS INTERFACE
The DSO uses a custom gate array to perform the I/O
expander bus interface function. All the control logic and com-
munication 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.
MODULE DATA
Function Code 83 (FC 83) in the control module configuration
accesses the DSO on the I/O expander bus. It also allows the
control module to automatically read status data from the I/O
module, and write output data to it. The I/O module address
in FC 83 must be the same as the address set on the digital
output module address dipswitch (S1).
