Fp Sync (With Speedlite 380 Ex) - Canon EOS 55 Service Manual

Part 2: Technical Information
2.11 FP Sync (with Speedlite 380 EX only)
1. Pre-flat* Firing
The MPU via the EFIC orders the flash to fire a "pre-flat" flash. Pre-flat flash power
and duration information is included. Immediately following the information transfer,
the trailing (falling) edge of the signal on STSP is used as the flash trigger.
2. Main Flat* Flash
The protocol for main flat-flash firing is the same as the pre-flat flash, but the trigger
timing is different. The STSP leading edge signal fires the flash which extends the
"flat firing" to cover the entire time span from the start of the first curtain run to the
end of the second curtain run.
3. Normal main flash is the same as previous EOS system flashes.
*· "Flat" flash is a series of limited flashes that combine to approximate the long low
output of the old FP flash bulbs for synchronizing with focal plane shutters. When
viewed on an oscilloscope it appears as a long flat pulse instead as the very short
peaky normal output of an electronic flash.
EF IC
MPU
OPAMP
Fig. 2-32 FP Sync
2-40
71
; RAE(RREQ)
: 47K
AE IC