DAC and PLL Programming
PCVisionplus
Hardware Reference
4–15
Rev 02; February 8, 2002
4.
Calculate the divider ratio for the feedback path:
Always set PDB to 1 (register value of 0x3) and find Fdiv using the following formula:
Fdiv = [Total number of pixels in horizontal period / 1]
or
Fdiv = [Fdesired / Horizontal Line Rate]
Fdiv = _____ / _______ = ______
Both give the same result. Set the FDIV register bits as follows:
FDIV = Fdiv – 1
FDIV = ______ – 1 = _______
5.
Set the following PLL reg bits as indicated:
PLLA0 = FDIV
PLLA1 and PLLA2 both = 0x0
PLLA3 = 0x400
RDIV=0 (Rdiv = 1 RDIV = Rdiv – 1 = 1 – 1 = 0 )
REF_POL = 1
PLLA4 = 0x75[1xxx] (where xxx = VCO calculated above)
VCO= from VCO Gain calculation above
PFD = 0x3 (PFD gain always set to 15uA/2pi-rad)
PDEN = 1 (phase detector enabled)
INTFLT = 0 (external loop filter selected)
CLKSEL = 1 (select OMUX0 as feedback source)
MSB = 1 (reserved bit must be 1)
PLLA5 = 0x5[11xx]3 (where xx= PDA bits form value found in tables)
FBKSEL = 1 (always select internal feedback)
FBKPOL = 1 (always select negative edge)
ADD = 0 (use default)
SWLW = 0 (use default)
PDA bits = Use value found in tables above.
PDB[0:1] = 0x3 (always use PDB = 1)
LDLG = 1 (use default)
FINEEN = 0 (use default)
MSB = 1 (reserved bit must be 1)
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