DESCRIPTION AND OPERATION
LOGIC POWER
WBPEEUI240755B0
2 - 7
The MFP reads a one byte value that consists of digital output
readback values and digital input values. The digital input val-
ues indicate the digital input states. Each bit corresponds to
one input; the bit value reflects the state of that input, either
open (logic 0) or closed (logic 1). Digital output readback data
reflects the output states. The MFP uses this data to verify that
the outputs are correct. Each bit corresponds to one output; a
logic 1 indicates an active (ON) output, a logic 0 indicates an
inactive (OFF) output.
Status Data
Status data is an 8-bit data value that identifies the I/O mod-
ule and indicates the default values set by the analog output
default jumpers. The MFP reads the identification bits (four
MSB) to verify the I/O expander bus communication integrity
and MFP configuration. It reads the default bits (four LSB) to
determine the default states set for the analog outputs in the
event of a
time-out.
LOGIC POWER
Logic power (+5 VDC and
±
15 VDC) drives the CIS and QRS
circuits. It connects through the top 12-pin card edge connec-
tor (P1) shown in Figure
. P3 su24 VDC to operate
the analog output circuits.
BUS FAULT TIMER
The bus fault timer is a one-shot timer that is reset by the I/O
expander bus clock; the MFP generates the bus clock. If the
bus clock stops (indicating a MFP error), the bus fault timer
times out
in 10 milliseconds. This will disable the digital out-
puts and set the analog outputs to their default values (set by
jumpers). A red front panel status LED indicates a bus fault
(
time-out
).
STATUS LED INDICATORS
Two front panel module status LED indicators show the oper-
ating state of the CIS and QRS modules. Circuits on the I/O
module determine the module status and light the appropriate
LED. Refer to
for explanations of the LED indications
and to
