Canon SPEEDLITE 540EZ Service Manual page 49

Part 2: Technical Information
4.14 Manual Flash
1) Manual Flash
(1) Pressing the mode switch informs pin No.70 of IC8 that the selected mode is the
manual mode.
(The default for this mode is 1/1, and the intensity level (1/1 to 1/128) can be
selected by the (+) and (-) switches.)
(2) The information of this mode is relayed from pins No.95 to 98 of IC8 to pins No.15
to 18 of IC7.
(3) When this information is received, IC7 informs pin No.2 of IC6 to use PD1.
(4) Releasing the camera causes the X and STSP signals from being input to pins No.8
and 10 of IC7.
(5) These signals cause the main flash trigger signal to be generated from pins No.35
and 36 of IC7 in order to start main flash. (For details, see 4.5 Main Flash.)
(6) When flash starts, the flash intensity is input to PD1.
(7) This information is sent to pin No.55 of IC7 to pin No.8 of IC6.
(8) IC7 compares this flash intensity and the set mode (intensity level). When the
intensity is appropriate, the flash stop signal is output from pin No.34 of IC7.
(9) This signal operates the flash stop circuit to stop flash.
(For details, see 4.6 Flash Control.)
2) Multi-flash
* Though multi-flash is basically the same as manual-flash above, the following points
are added.
(10) Pressing the mode switch twice causes the multi-flash mode to be entered to IC8.
This information is also relayed to IC7.
(11) By this, IC7 learns that the mode is the multi-flash mode.
(12) When the flash signals (X and STSP) are sent from the camera, the trigger signal
matched to the multi-flash mode is repeatedly output from IC7, and multi-flash is
carried out.
(Stopping multi-mode flash is the same as that for the manual flash mode.)
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