Canon A-1 Repair Manual page 135

. ...
I
. .. .
zv
Word 2 Binary: 00111100
~
Octal Code 074 (from the
AV Code Table)
OCtal 074 - f/9.5
Note: The 0 BUS information is rounded off to the
nearest 1/2 step because it 1s the input infor-
mation to the display decoder driver IC. The
actual working outputs to the OSC/lnterface IC
are stepless in principle (actually 1/8 EV
steps)".
*: The control should be refered to as stepless in
information released to the public.
As stated before, T.80 and T.B 1 are disregarded
when converting from binary to octal code. In the
AV word they actually serve a different function.
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(Camera: AV Priori ty Mode)
(Tool & Trigger: Bus Checker)
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,
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0', .
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When the camera is in AV
pri ori ty mode, T.B 0 and
T. B 1 do carry shutter
speed information although
it is modified for rounding
off the display information
to the nearest 1 / 2 step
shutter speed.
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IV
.
-
.. ..
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,
.. .. .. . .
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For example, in figure 3-30
word 2 is 00110010 which
converts to octal code 114
or f / 19.
Fig. 3-30
Word 1 indicates the shutter speed calculated by the
camera. Using the entire binary 10010001 converts to
octal 211 which is the modified code to round off the
display. To find the actual shutter. speed, subtract
octal 002 from the octal code. In this case the true
shutter speed is octal 207 which is 1/8 step slower
than octal code 210 which is 1/250 second .
Note: The above method of calculation can be used, but
the method used in explaining Fig. 3-29 where
T.B
a
and T.B 1 are considered as "00" is
simpler and less prone to error.
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