Epson PX-8 - Page 114

REV.-A
~- 2.9.3.2 Processing By Sub-CPU After Detection
The sub-CPU 7508 converts the ANO voltage to a digital value based on the reference voltage.
The sub-CPU
then finds the points that correspond to 25°C and 45°C, and controls the D-RAM re-
fresh
current for saving power consumption as follows:
< Temperature range (0C) > < D-RAM refresh current (,uA) >
45 or above................................... 1400
25 or above........... ........................ 600
Below 25 ... ...... ... ... ........................ 300
2.9.4 Analog Input (ANIN)
The Analog Input (ANIN) terminal in the analog input interface, which is connected to the AN2 ter-
minal of the A-D converter, provides a universal A-D conversion capability which can convert any
analog
voltage signal from OV to +2V to digital data from 00 (H) to FF (H). A triggering output
(TRIG) terminal is provided in this interface so that a wide variation of analog devices from a sim-
ple one such as a joystick to a complicated measurement instrument can be connected. The ANIN
signal line
may be pulled up to the +5V supply via the jumper J4.
The input signal is limited from OV to +5V by voltage limiter diodes, and high frequency noises on
the signal line are removed by a filter circuit, including the capacitor C37, before being connected
to the A-D converter. Fig. 2-92 shows the barcode control circuit.
Analog input interface
Barcode interface
R52
TRIG
10K
ANIN
+5
C33~
R107
GND+
100K
0A2
RM1-1
R33
J4
I I
P
10K 5.1K
ON II OFF
OAl
C31
R106
100K
+5
07
R49
R56
R32
BRDT
10K 10K
5.1K
07
C321
C361
R23
2.2K
2
Q10
VB
+5
3
Go--- ....
BCD
(4C)
12
5
120
Fig.
2-92 Barcode Control Circuit
2-90
P62
AN2
AID converter
AN3
(1 D)
,uPD7001