Canon 580EX - Speedlite II - Hot-shoe clip-on Flash, Service Manual

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Technical Information
9
(5) If that output signal is "H", FET1 turns ON, and Q8 urns on turn IT1 ON.
As a result, Xe1 fires, If that output signal is "L", FET1 turns OFF, Q16 turns ON and IT1
turns OFF to stop firing.
<Operation Sequence>
(1), (2)
(3) → (4) → (5)
↑
Repeated for the time indicated from the camera (flat firing)
3) Flash Firing
(6) If "L" outputs from IC107pin 41, the voltage corresponding to the firing intensity in the
flash firing mode is generated at the IC102S internal integration circuit by the metering
sensor selected by IC20. (ABOUT)
(7) That voltage is compared with the firing control value (A/D converter voltage). If the
voltage is lower, "H" is output to IC102S pin 17. If it is higher, "L" is output. Either of "H"
or "L" is input to IC107S pin 46 (A/D detection terminal), and the firing integrated value
is checked internally by IC107S.
<Operation Sequence>
(1), (2)
(6) → (7) → (5)
4) TTL Firing
(8) The signal (STSPC input) from the camera is input to IC102S pin 25 and the firing is
turned on or off. It is input also into pins 16 and 99 of IC107S from IC102S pin 13, and
"H" and "L" of STSPC are checked.
(9) If STSPC becomes "H" within 4 ms after the flash fires, PD5 is turned on for 3 seconds.
(Flash exposure confirmation)
<Operation Sequence>
(1), (2)
(8) → (5) → (9)
5) External Flash Metering
(10) If IC107S outputs "H", voltage corresponding to the signals (reflected light from subjects)
from optical sensor of PD11 selected by IC20 is generated in integrating circuit inside
IC102S.
(11) That voltage is compared with the firing control value (A/D converter voltage). If the
voltage is lower, "H" is output to IC102S pin 17. If it is higher, "L" is output. Either of "H"
or "L" is input to IC107S pin 46 (A/D detection terminal), and the firing integrated value
is checked internally by IC107S.
<Operation Sequence>
(1), (2)
(10) → (11) → (5)