Canon SPEEDLITE 540EZ Service Manual page 47

Part 2: Technical Information
4.11 SE Timer
(2) Restart is carried out by pressing the test button, or pin No.29 of IC7 becoming
Low due to the signal (High signal on TV line) from the camera.
(3) This signal changes the state of pin No.87 of IC8 to Low.
(4) This changes the state of pin No.13 of IC8 from High to Low, and restarts
oscillation.
¢ Flow of Operation: (1) > (2) > (3) > (4)
Figure 2-16 Circuit 11
4.12 Temporary Mode Memorization
The set flash mode is memorized for 90 seconds even if the batteries are replaced with
the main switch turned OFF (or, in the SE mode). The following describes circuit
operation at this time.
(See Figure 2-16 for details on the circuit diagram.)
(1) As pin No.13 of IC8 is High when the main switch is OFF, or when the camera is in
the SE mode, RQ2, RQ9 and RQ14 are OFF. VDD output from pin No.5 of IC1 is
not supplied to the flash control circuit, and is supplied only to pin No.81 of IC8.
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