DESCRIPTION AND OPERATION
ANALOG I/O
WBPEEUI240755B0
2 - 3
Analog Input Circuit Calibration
The reference block generates accurate 1 VDC and 5 VDC sig-
nals. The I/O module does not have potentiometers to adjust
zero offset and gain for the A/D converter circuits. Instead, the
MFP reads the reference voltages once per minute to calibrate
the zero percent (1 VDC) and 100 percent (5 VDC) points; this
calibration automatically corrects the measured values. It is
performed continuously to correct for drift and temperature
variations.
Analog Outputs
The D/A converter block is two separate D/A converters
(Figure
). A 4-bit microcontroller converts and checks data
integrity from the MFP. Each D/A converts a 10-bit digital
value (analog count) from the microcontroller to an analog
output (one to five VDC). To check module circuit integrity,
the outputs are fed back to the analog input section. The
feedback values (analog output digital values) are compared
to the values that were sent to the analog output section to
test the output quality. This tests for an output circuit failure
or an open loop between the control module and I/O module.
The analog output default jumpers set the output values dur-
ing system start-up or
time-out
(refer to
this section). The analog outputs will go to zero percent or 100
percent output, or they will hold their current values depend-
ing on the setting of the default jumpers. Refer to
put Default Jumpers (J7, J8, J12, J14, J10, J16)
Section 3 for details.
NOTE: All the analog output activities are under microcontroller con-
trol.
Figure 2-3. Analog Output Circuit Example
FROM D/A
CONVERTER
FEEDBACK
–
+
+
–
3
6
1
7
-15 V
+24 V
2
5
1
2
3
T00323A
J9
J11
