DESCRIPTION AND OPERATION
MODULE DATA
I-E96-207A
2 - 7
Digital Outputs
The output isolation block consists of optocouplers to isolate
the control logic circuits from the process. Four open collector
transistors that can sink a 150 mA load make up the driver
block.
Digital I/O Buffer
The digital I/O buffer block is a buffer and register that holds
the values of the digital inputs and outputs. The digital output
interface writes digital data to the register for output by the
driver block circuits, and reads the digital input values from
the buffer.
I/O Circuit Connections
The I/O signals connect to the 30-pin card edge connector P3
of the COM using a termination cable from a TU/TM. It also
su24 VDC power to operate the analog output circuits.
MODULE DATA
COM address switch configuration sets the address on the
module bus. It also allows the COM to read input data or sta-
tus data from master modules, and write output data to them.
This data is output by buffer circuits to the module bus inter-
face (see Figure
). Set the module bus address on dipswitch
S4.
I/O Data
I/O data is analog input, digital input, and digital and analog
output values that the COM reads from the field devices. It is
also analog and digital output values that the COM sends to
other master modules. The other master modules may use this
data to monitor and control a process, and verify COM
operation.
Analog input data consists of analog counts from the A/D con-
verter. Analog counts are digital values that correspond to ana-
log signals; the A/D performs the conversion. The signals
converted include the four analog inputs, two reference volt-
ages (1 VDC and 5 VDC) and two analog output readback val-
ues. The COM reads each of these count values once every
execution cycle. Each analog input count value correspond to
an analog input voltage. Reference voltage values are read by
the COM to verify A/D converter integrity. It reads the two ana-
log output values to adjust the analog outputs and check for
output circuit failures.
