ADSP-BF50x Blackfin Processor Hardware Reference
8-5
Dynamic Power Management
The PLL control (
PLL_CTL
) register controls operation of the PLL (see
Figure 8-4 on page 8-21
). Note that changes to the
PLL_CTL
register do
not take effect immediately. In general, the
PLL_CTL
register is first pro-
grammed with a new value, and then a specific PLL programming
sequence must be executed to implement the changes. This is handled
automatically by the system control ROM function (
bfrom_SysControl()
)
as described in
“System Control ROM Function” on page 8-23
.
Core Clock/System Clock Ratio Control
Table 8-2
describes the programmable relationship between the VCO fre-
quency and the core clock.
Table 8-3
shows the relationship of the VCO
frequency to the system clock. Note the divider ratio must be chosen to
limit the
SCLK
to a frequency specified in the processor data sheet. The
SCLK
drives all synchronous, system-level logic.
The divider ratio control bits,
CSEL
and
SSEL
, are in the PLL divide
(
PLL_DIV
) register. For information about this register, see
“PLL_DIV
Register” on page 8-20
.
The reset value of
CSEL[1:0]
is 0x0, and the reset value of
SSEL[3:0]
is
0x4. These values can be reprogrammed at startup by the boot code.
By updating
PLL_DIV
with an appropriate value, you can change the
CSEL
and
SSEL
value dynamically. Note the divider ratio of the core clock can
never be greater than the divider ratio of the system clock. If the
PLL_DIV
register is programmed to illegal values, the
SCLK
divider is automatically
increased to be greater than or equal to the core clock divider.
63
63x
31.5x
0
64x
32x
Table 8-1. MSEL Encodings (Cont’d)
Signal name
VCO Frequency
MSEL[5:0]
DF = 0
DF = 1
Summary of Contents for EZ-KIT Lite ADSP-BF506F
Page 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Page 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...