Clocking
8-6
ADSP-BF535 Blackfin Processor Hardware Reference
The System Select field (
SSEL[1:0]
) of the PLL Control Register
(
PLL_CTL
) controls the ratio of
CCLK
to
SCLK
. Upon reset, the input pins
SSEL[1:0]
are sampled. (These pins are shared with flag input pins
PF[9:8].
)
The values on
SSEL[1:0]
determine the initial system clock ratio.
To change the
CCLK-SCLK
divider ratio, the
SSEL
field in the
PLL_CTL
regis-
ter should be modified with the new value. This field can be changed at
any time, but changes to the divider ratio do not take effect until the PLL
programming sequence is executed. See
“PLL Programming Sequence” on
page 8-17
.
The user should ensure that peripheral operation does not suffer
adverse effects when the system clock ratio is changed.
Table 8-2
shows the system clock ratio, or frequency ratio of
SCLK
relative
to
CCLK
.
Table 8-2. System Clock Ratio
Signal Name
Divider Ratio
Example Frequency Ratios
(MHz)
SSEL[1:0] CCLK/SCLK
CCLK
SCLK
00 2:1
266
133
01 2.5:1
275
110
10
3:1
300
100
11
4:1
300
75
Summary of Contents for ADSP-BF535 Blackfin
Page 80: ...Development Tools 1 26 ADSP BF535 Blackfin Processor Hardware Reference...
Page 312: ...Working With Memory 6 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 332: ...System Interfaces 7 20 ADSP BF535 Blackfin Processor Hardware Reference...
Page 360: ...Dynamic Power Management Controller 8 28 ADSP BF535 Blackfin Processor Hardware Reference...
Page 446: ...Beginning and Ending an SPI Transfer 10 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 522: ...Timing Examples 11 76 ADSP BF535 Blackfin Processor Hardware Reference...
Page 562: ...IrDA Support 12 40 ADSP BF535 Blackfin Processor Hardware Reference...
Page 608: ...PCI I O Issues 13 46 ADSP BF535 Blackfin Processor Hardware Reference...
Page 672: ...References 14 64 ADSP BF535 Blackfin Processor Hardware Reference...
Page 810: ...SDRAM Controller SDC 18 86 ADSP BF535 Blackfin Processor Hardware Reference...
Page 811: ...ADSP BF535 Blackfin Processor Hardware Reference 18 87 External Bus Interface Unit...
Page 812: ...SDRAM Controller SDC 18 88 ADSP BF535 Blackfin Processor Hardware Reference...
Page 860: ...DMA Bus Debug Registers 20 30 ADSP BF535 Blackfin Processor Hardware Reference...