PCVisionplus
Hardware Reference
Registers
3–65
Rev 02; February 8, 2002
3.5.1.2 Frame Count (FCNT) R/W
The three FCNT bits determine the number of images stored in memory after each acquire command (snap, grab, or
triggered acquire). The FCNT bits allow up to eight images. The image size also determines the number of images
that will fit into a 4MB memory frame.
FCNT
Function
0
Acquire 1 image
1
Acquire 2 images
. . .
. . .
7
Acquire 8 images
A snap command or triggered snap acquires FCNT number of images and stops. A grab command or triggered grab
stores FCNT images before wrapping back to the acquire start address and continuing to acquire.
3.5.1.3 Starting Field Select (FLDSEL) R/W
The two FLDSEL bits determine which field of an interlaced image will begin the acquire cycle. Program FLDSEL
to zero for non-interlaced images.
FLDSEL1
FLDSEL0
Function
0
0
Start acquire on next field
0
1
Reserved
1
0
Start acquire on next even field
1
1
Start acquire on next odd field
3.5.1.4 Acquire Command (ACQMD) R/W
The two ACQMD bits initiate the various camera acquisition modes into image memory, and also indicate when an
acquisition has ended.
ACQMD
Function
0
Freeze (stop acquire)
1
Invalid
2
Snap (single frame acquire)
3
Grab (continuous acquire)
These bits change immediately when they are written, however they are sampled with vertical blank or trigger. The
start of an acquire is sampled at the end of vertical blank and the end of an acquire is sampled at the beginning of
vertical blank. An acquire starts at the end of the next vertical blank.
If the two ACQMD bits are both 1, the acquire will be continuous grab. During a grab the ACQMD bits will be read
back as a 3 until either a snap or freeze command is issued.
If the ACQMD bits are programmed to 2, the acquire will be a single frame snap. During a snap the ACQMD bits will
be read back as a 2 until the acquisition is complete. Non-interlaced acquisition completes at the start of next vertical
blank. Interlaced acquisition completes at the start of the second vertical blank.
A freeze command will terminate an acquisition at the start of the next vertical blank. After a freeze command the
ACQMD bits will be read back as 0 immediately, however the acquire will not actually end until the start of the next
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