Siemens SXG 75 Service Repair Documentation page 61

When flash operation is required on the Samsung mega pixel camera, the VSYNC output becomes
active earlier than normal. This extended pulse is used to synchronise the external flash to the time
when the camera pixels are active.
When the camera shutter is activated, The MSM6250 needs to enable one full V-sync pulse during
the active camera period. So it must monitor the vertical synchronization signal CAMIF_VSYNC and
enable FLASH_EN after a falling edge of CAMIF_VSYNC, as shown below. The DCD pin of UART1
(MSM_UART1_DCD_N) is also tri-stated during this period since this pin is also connected to the
DCD/CLK pin of the accessory connector (flash trigger pin).
Camera flash trigger signal
The arrangement provided below allows the flash trigger (CLK/DCD) to be driven by the
CAMIF_VSYNC line from the mega pixel camera whilst being controlled by the MSM6250. The clip
on flash will only receive the VSYNC trigger pulse when the CAMIF_VSYNC line is high, and
FLASH_EN trigger line is low.
The MSM6250 can thus enable the sync pulse by taking FLASH_EN (GPIO64) low, and setting
MSM_UART1_DCD_N to tri-state.
Camera flash trigger circuit
Technical Documentation
TD_Repair_L3_SXG75_R1.0.pdf
Company Confidential
2006©BenQ
Release 1.0
01/2006
Page 61 of 73