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P5040/P5020 Reference Design Board User Guide, Rev. 0
Freescale Semiconductor
55
Programming Model
7.1.8
Speed Register (PX_SPD)
The speed register communicates current switch-selectable settings for the SYSCLK clock generator.
PX_SPD enables software to accurately initialize timing-dependant parameters for local bus, DDR
memory, I
2
C clock rates, and so on.
Figure 29. Speed Status Register (PX_SPD)
0
1
2
3
4
5
6
7
R
—
—
—
—
—
SYSCLK
W
Reset
X
X
0
0
0
X
X
X
Offset
0x07
Table 34. PX_SPD Field Descriptions
Bits
Name
Description
0–1
PIXISOPT
Reflects SW12(1-2) settings.
2-4
—
Reserved (0)
5–7
SYSCLK
Reflects SW5(6-8) settings; see
Table 35. SYSCLK Frequency Options
SYSCLK
(PX_SPD[5:7])
Actual
SYSCLK
Nominal
SYSCLK
Error
ICS307
Control Word
0 0 0
66.666 MHz
67 MHz
4.985 ppm
0x370801
0 0 1
83.333 MHz
83 MHz
4.012 ppm
0x330601
0 1 0
100.000 MHz
100 MHz
0 ppm
0x330801
0 1 1
125.000 MHz
125 MHz
0 ppm
0x310381
1 0 0
133.333 MHz
133 MHz
2.503 ppm
0x310401
1 0 1
150.000 MHz
150 MHz
0 ppm
0x310501
1 1 0
160.000 MHz
160 MHz
0 ppm
0x310C03
1 1 1
166.666 MHz
167 MHz
2 ppm
0x310601