Circuit Operation (Signals And Waveforms) - Canon A-1 Repair Manual

3. Circuit Opera tion (Signals and Waveforms)
The A-l electronic circuit is very complicated in principle,
but, in actual practice, if the inputs and outputs from
each IC pin are known most problems can
be
readily under-
stood .
This section of the Repair Guide list the singals present
at each pin (or leg) of each IC. Illustrations of
oscilloscope waveforms and codes shown on the BUS CHECKER
(Tools Instruction No . F-050E) are given, as well as voltage
levels, possible problems and other useful notes . A low
voltage power supply set at five volts was used for all
test.
Almost all signals depend on the timing of the synchroniza-
tion trigger (SYNC (07». See section 3.3.17 to check it.
Notes: Oscilloscope displays and the Bus Checker both
have the least significant digit (LSD) at the left
and the most significant digit (MSO) at the right.
The time base (TB) position numbers indicate the
power to which the radix 2 is raised. For this
reason, the binary code is converted to octal code
as illustrated in the example below.
Sample
All measurable data is presented 1n "active low"
configuration. In other words, the ground, or
lower, level 1s a "lit and the higher level 1s a
"0".
It is necessary to remember this when reading
waveforms on the oscilloscope.
Ghowing LED's shall be read as "1" and dark LED's
shall be read as ·0". The LED's are grouped from
the left side in groups of three LEOs, three LEOs,
and two LEOs. Read the code "1" or "0" according
to which LEO's are lit, respectively, and the
numeral indicated below each LED, then, find total
figures from each group to obtain a three digit
figure comprising one each numeral of each of
three groups, and reverse the order of the numerals
as illustrated in the following diagram .
case
,
"
"
,
,
'
.
., I "
-0 -
0
- 0 - 0
-0- 0 -0-
0
,
,
.
,
.
,
'
,
1
2
4'
1
2
4
'l.
2
lxl 2xO 4xl
lxO 2xl 4xO
lxl 2J<0
0
,
-
J
\
I
,
-
5
2
1
1
2
5
-
125
53