Canon A-1 Repair Manual page 137

13. AECG (l3P)
1.0-1.2V
OV
Fig. 3-33
14.
SYNC . (07) (14P)
Fig . 3-34
AE Charge Signal
This signal is the input
which tells the CPU that
the AE mechanism is charged.
When charged, this point
is grounded giving a low .
Since the unit works on
"active low", this 1s a
"1" . If not charged ap-
prox.
IV
is present .
(Trigger: 07 leading edge,
negative going)
SYNC (07) is the system
trigger. It is used as the
trigger for the bus checker
and most oscilloscope
checks. It is available
on a test pad on the ridge
over the pentaprism.
Figure 3-34 is the 07 wave-
form. There are 8 bits 1n
one cycle of the 07 wave-
form, · n umbered from the
left T.B 0 thru T.B 7.
The last bit (07) is a low
and the others are all highs.
Since this unit uses eight
bit words, T.B 0 thru T.B 7
define one word . When 1
looking at "wordforms",
it
is convenient to take the
oscilloscope time base off
the calibrated position and
adjust the sweep length
so one bit is one scale
divis~on
long on the display.
(When this is
marked
> 20~S
done on the example waveforms they are
in the upper right corner.)
This 07 leading edge trigger was used in the example
above, but the trailing edge (positive going) trigger
is useful for many test.
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