402-00005-00
DAC and PLL Programming
4–22
Rev 02; February 8, 2002
Interlaced: VTOTAL = [( ______ / 2) – .5 ] x 2 = _____
for Non-interlaced: VTOTAL = [(Total lines per frame ) – .5 ] x 2
Non-interlaced: VTOTAL = [( ______ ) – .5 ] x 2 = _____
VSEND = ( # of lines in Vsync – .5 ) x 2
VSEND = ( ______ – .5 ) x 2 = _______
For RS-170:
horizontal lines time = 63.556 us
hsync time = 4.7 us
Total lines per frame = 525
Total lines per field = 525/2 = 262.5
Lines in vertical front porch = 3
Lines in Vsync = 3
For CCIR:
horizontal lines time = 64us
hsync time = 4.7us
Total lines per frame = 625
Total lines per field = 625/2 = 312.5
Lines in vertical front porch = 2.5
Lines in Vsync = 2.5
4.4.1 Notes on Programming XTAL Mode
Many video sources vary slightly from the defined RS-170/CCIR values which will require fine tuning of the PWG
and PLL settings. Rounding errors can also occur, causing the pixel clock (Pclk) value to be off slightly from the
desired value.
Once the register settings are programmed, the user can check the image being acquired and verify the correct num-
ber of samples per line/frame are being captured. Specifically check the start and end of the horizontal line and verify
valid pixel data is present (this can be done by saturating the video source). Two adjustments can be made to compen-
sate for discrepancies. First the HOFF and HACTIVE values can be changed to move the ACTIVE video window
left or right and the video is then re-checked. If there is no combination of HOFF and HACTIVE which compensate
for differences, the Fdiv value can be increased or decreased which will cause the Pixel clock rate to increase or
decrease slightly giving larger or smaller samples.
When programming the PLL registers, the ideal is to program the pixel clock to exactly match the active video region
of the camera. As you change the pixel clock value, the number of pixels sampled within the fixed total line time (or
fixed active time) will vary. Slight oversampling within the active region can also be used to establish a desired reso-
lution. For example, you want 640 pixels within the active video region of a RS-170 camera. Set the desired number
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