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Intel® PXA26x Processor Family Developer’s Manual 3-5
Clocks and Power Manager
3.3.4 95.85-MHz Peripheral Phase Locked Loop
The 95.85-MHz PLL is the clock source for many of the peripheral blocks’ external interfaces.
These interfaces require: ~48 MHz for the UDC/USB,
fast infrared communications port (FICP),
~33 MHz for the I
2
C, and ~20 MHz for the MMC. The generated frequency is not exactly the
required frequency due to the chosen crystal and the lack of a perfect least common multiple
between the units. The chosen frequencies keep each unit’s clock frequency within the unit’s clock
tolerance. If a crystal other than 3.6864 MHz is used, the clock frequencies to the peripheral
blocks’ interfaces may not yield the desired baud rates (or protocol’s rate).
Table 3-1. Core PLL Output Frequencies for 3.6864-MHz Crystal
LM
Turbo Mode Frequency (MHz) for Values
“N” and Core Clock
Configuration Register (CCCR[15:0])
programming for Values of “N”:
PXbus
Frequency
(MHz)
MEM, LCD
Frequency
(MHz)
SDRAM
max Freq
(MHz)
1.00
(Run)
1.50 2.00 3.00
27 1
99.5
@.85 V
—
199.1
@1.0 V
298.6
@1.1 V
50 99.5 99.5
32 1
118.0
@1.0 V
—
235.9
@1.1 V
353.9
@1.3 V
59 118.0 59.0
36 1
132.7
@1.0 V
—
265.4
@1.1 V
398.1
@1.3 V
66 132.7 66
40 1
147.5
@1.0 V
—
294.9
@1.1 V
— 74 147.5 74
45 1
165.9
1.0 V
—
331.8
1.3 V
— 83 165.9 83
27 2
199.1
@1.0 V
298.6
@1.1 V
398.1
@1.3 V
— 99.5 99.5 99.5
32 2
235.9
@1.1 V
— — — 118 118.0 59.0
36 2
265.4
@1.1 V
— — — 132.7 132.7 66
40 2
294.9
@1.1 V
— — — 147.5 147.5 74
45 2
331.9
@1.3 V
— — — 165.9 165.9 83
27 4
398.1
@1.3 V
— — — 200 99.5 99.5
Table 3-2. 95.85-MHz Peripheral PLL Output Frequencies for 3.6864-MHz Crystal
Unit Name Nominal Frequency Actual Frequency
USB (UDC) 48 MHz 47.923 MHz
FICP 48 MHz 47.923 MHz
I
2
C 33 MHz 31.949 MHz
MMC 20 MHz 19.169 MHz