PCVisionplus
Hardware Reference
Theory of Operation
2–39
Rev 02; February 8, 2002
instead require the frame reset to occur by simply pulling the vertical sync input to the reset state, which is accom-
plished by this PTG feature. Some cameras require no vertical sync when in frame reset mode, which can be accom-
modated using the VSYNCEN bit to disable the PTG vertical sync output when in frame rest mode. The Hsync is not
reset in this mode because frame reset does not require the horizontal timing to be reset. Using frame reset in PLL
mode, incoming Hsync is not reset by the frame reset signal; therefore maintaining horizontal line lock.
RGB Video
VBLANK
HBLANK
Trigger Input
FRST (1 line)
FRST
TRGEN0
Strobe
TRGCYC0
PTG Vsync
FROFF
(Froff mode)
STRBDLY
FIFO Load
Figure 2–37. Triggered Acquire in Frame Reset
In Figure 2–37, the external trigger pulse immediately causes a Frame Reset pulse (FRST). The pulse duration is one
line or the number of lines in the FROFF register. A strobe occurs immediately, or at the end of the STRBDLY count.
The strobe output follows the same rules as Fast Strobe mode. STRBDLY is commonly increased to compensate for
the FROFF delay. In XTAL mode the PTG Vsync is reset by FRST. The Frame Reset pulse resets the camera, forcing
the camera video output into vertical blank. One line after the frame reset pulse TRIGCYC is set high and TRIGEN is
cleared, indicating the acquire cycle has begun.
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