Canon A-1 Repair Manual page 33

values but the values will not be completely stepless
as in the case of analog system.
(3) Circuit Component
One IC and four LSI are used in the A-l's electronic
circuit.
OPT IC:
The HOS-BI log amplifier is integrated with the SPC
and sealed into a single IC. The IC used in the A-l
has a wider metering range than the one in the AE-l.
INPUT Ie:
This is an 12L with an internal layer insulation.
It .is used in the area of information input. This is
part of the LSI design where analog and digital
circuit are on the same chip as isolated 12L, and
includes the AD converter.
CPU IC:
This is an LSI consisting of pure 12L and including
the CPU. As this LSI is composed of digital circuits,
only greater c ircuit densi ty is achieved. As
in~ula­
tion between analog and digital circuits is not neces-
sary, density can be increased proportionally.
In the LSI
built-in.
12L.
of the A-l, an a-bit micro-computer is
Fig. a shows the construction of the pure
OSC/INTERFACE:
This is a bi-polar Ie consisting of oscillator and
interface circuits. In this section, high
stabilit~
oscillator, a magnet which activates at a constant
current, and driver to activate the LED are built in.
DECODER DRIVER:
This Ie is an LSI of 12L (isolated 1 2 L) with internal
insulated layer used in the decoder driver section.
Here too, a 'constant current LED driver is built in
to give advantage of reduction in the number of parts
and savings in the consumption of electricity.