CY28325PVC-2 Cypress Semiconductor Corp., CY28325PVC-2 Datasheet - Page 14

• Manufacturer Part Number: CY28325PVC-2
• Description: Frequency Timing Generators For PC And Server Motherboards
• Manufacturer: Cypress Semiconductor Corp.

Program the CPU output frequency
When the programmable output frequency feature is enabled
(Pro_Freq_EN bit is set), the CPU output frequency is deter-
mined by the following equation:
Fcpu = G * (N+3)/(M+3).
“N” and “M” are the values programmed in Programmable
Frequency Select N-Value Register and M-Value Register,
respectively.
Table 5. Examples of N and M Value for Different CPU Frequency Range
Document #: 38-07119 Rev. *A
Frequency Ranges
130 MHz–248 MHz
50 MHz–129 MHz
Gear Constants
48.00741
48.00741
PRELIMINARY
M-Value Register
Fixed Value for
93
45
“G” stands for the PLL Gear Constant, which is determined by
the programmed value of FS[4:0] or SEL[4:0]. The value is
listed in Table 4.
The ratio of (N+3) and (M+3) need to be greater than “1”
[(N+3)/(M+3) > 1].
The following table lists set of N and M values for different
frequency output ranges.This example use a fixed value for
the M-Value Register and select the CPU output frequency by
changing the value of the N-Value Register.
for Different CPU Frequency
Range of N-Value Register
127 - 245
97 - 255
CY28325-2
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