General Standards Corporation PCIe-24DSI32, Reference Manual

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PCIe-24DSI32
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3-12
Table 3.6.2.1-1. PLL Nref Register
Offset: 0004h Default: 0000 01F4h
BIT FIELD MODE DESIGNATION FUNCTION
D[09..00] R/W
REF FACTOR (Nref)
PLL Reference factor; 30-1000.
D[31..10] R/W (Reserved) ---
Table 3.6.2.1-2. PLL Nvco Register
Offset: 0008h Default: 0000 01F4h *
BIT FIELD MODE DESIGNATION FUNCTION
D[09..00] R/W VCO FACTOR (Nvco) PLL VCO factor; 30-1000.
D[31..10] R/W (Reserved) ---
NOTE: Nvco and Nref each has a maximum range from 30 to 1000. For optimum
performance, select the
lowest possible values for Nvco and Nref.
Because specific applications might require custom values for Fref , an approximate
measurement of the installed PLL reference oscillator frequency is available in the
PLL Reference Freq register listed in Table 3.1. This value is determined at initialization, and
equals
Fref in Hertz with an accuracy of approximately 0.02-percent. It is intended as an
indicator only, and is not recommended as a source for the actual Fref frequency.
By combining Equation 3-3 with Equation 3-1 in Section 3.6.1.3:
(3-4)
Table 3.6.2.1-3. Summary of PLL Sample Rate Control Parameters
PARAMETER NOTATION RANGE
VCO Frequency Range Fgen 20-55 MHz
VCO Factor Nvco 30-1000
Reference Factor Nref 30-1000
Rate Divisor Ndiv 0 - 25
Reference Frequency Fref Standard value = 32.768MHz
Fsamp * 512 * DIVISOR
Fref (32.768MHz)
Nvco
Nref
=
.