95.85 Mhz Peripheral Phase Locked Loop; Core Pll Output Frequencies For 3.6864 Mhz Crystal; Mhz Peripheral Pll Output Frequencies For 3.6864 Mhz Crystal - Intel PXA255 Developer's Manual

Table 3-1. Core PLL Output Frequencies for 3.6864 MHz Crystal
L
27
36
27
36
45
27
Note: These are the only supported frequency settings.
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
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 3-2. 95.85 MHz Peripheral PLL Output Frequencies for 3.6864 MHz Crystal
Unit Name
USB (UDC)
FICP
2
I C
MMC
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
2
(I 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
Intel® PXA255 Processor Developer's Manual
Turbo Mode Frequency (MHz) for Values
"N" and Core Clock
Configuration Register (CCCR[15:0])
programming for Values of "N"
M
1.00
1.50
(Run)
99.5
1 —
@1.0 V
132.7
1 —
@1.0 V
199.1 298.6
2
@1.0 V @1.1 V
265.4
2 —
@1.1 V
331.8
2 —
@1.3 V
398.1
4 —
@1.3 V
Nominal Frequency
PXbus
Frequency
(MHz)
2.00 3.00
199.1 298.6
50
@1.0 V @1.1 V
— — 66
398.1
— 99.5
@1.3 V
— — 132.7
— — 165.9
— — 196
48 MHz
48 MHz
33 MHz
20 MHz
Clocks and Power Manager
SDRAM
MEM, LCD
max
Frequency
Frequency
(MHz)
(MHz)
99.5 99.5
132.7 66
99.5 99.5
132.7 66
165.9 83
99.5 99.5
2
C), and ~20 MHz (MMC). The
Actual Frequency
47.923 MHz
47.923 MHz
31.949 MHz
19.169 MHz
3-5