Epson PX-8 - A-D Converter,Upd7001

REV.-A
7.7 A-D Converter ,uPD7001
The ,uPD7001 is an 8-bit, C-MOS serial output, analog-to-digital converter which incorporates a
4-channel analog
input multiplexer. In this computer, the reference voltage is set to +2.0V, pro-
viding an effective resolution of the upper six bits. The LSB corresponds to approximately O.03V.
It employs a sequential comparison A-D conversion method, and requires a conversion time of
140,us.
The computer assigns the analog input channels for battery voltage sensing, temperature sensing,
barcode
data input, and external analog signal input. Fig. 7-15 is a functional block diagram and
Fig. 7
-16 outlines the timing relationships among the operating signals.
Timing chart
CS
SO/EOC
SCK
SI
VDD DL SI SCK SO EOC
Analog
input
channels
o 0--+---1
20---+--1 plexer
30--+---1
Reference
input
Analog 0---+--'---...,.--'
GND
9-bit shift
register
0-+--0 CS
~-I--.QCLO
Sequence
controller ~-I--.Q CLl
Fig. 7-15 A-D Converter ,uPD7001 Block Diagram
_LSB----Jf
;
I
i
,
;)'
Invalid
Invalid
It
Dl Do
(Dl, Do
SI terminal - shift register)
(Dl, Do
shift register - address latch)
Fig. 7-16 A-D Converter Operation Timing Chart
7-34