4 95.85mhz peripheral phase locked loop, 5 147.46mhz peripheral phase locked loop, 85 mhz peripheral phase locked loop -5 – Intel PXA255 User Manual
Page 67: 46 mhz peripheral phase locked loop -5, Table 3-1, “core pll output frequencies for, 6864 mhz crystal
Intel® PXA255 Processor 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 (UDC/USB, FICP), ~33 MHz (I
2
C), and ~20 MHz (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).
3.3.5
147.46 MHz Peripheral Phase Locked Loop
The 147.46 MHz PLL is the clock source for many of the peripheral blocks’ external interfaces.
These interfaces require ~14.75 MHz (UARTs), 12.288 MHz (AC97), and variable frequencies
(I
2
S). The generated frequency may not exactly match the required frequency due to the choice of
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 other protocol’s rate)
Table 3-1. Core PLL Output Frequencies for 3.6864 MHz Crystal
L
M
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
Frequency
(MHz)
1.00
(Run)
1.50
2.00
3.00
27
1
99.5
@1.0 V
—
199.1
@1.0 V
298.6
@1.1 V
50
99.5
99.5
36
1
132.7
@1.0 V
—
—
—
66
132.7
66
27
2
199.1
@1.0 V
298.6
@1.1 V
398.1
@1.3 V
—
99.5
99.5
99.5
36
2
265.4
@1.1 V
—
—
—
132.7
132.7
66
45
2
331.8
@1.3 V
—
—
—
165.9
165.9
83
27
4
398.1
@1.3 V
—
—
—
196
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