Intel® PXA255 Processor Developer’s Manual 3-39
Clocks and Power Manager
3.7.1 Core Clock Configuration Register (CCLKCFG)
The CCLKCFG register ( CP14 register 6), show n in Table 3 -24, is used to enter the turbo mode
and frequency change sequence. To enter the mode or sequence, software executes the ap pr opriate
function from Tabl e 3-23. All core-initiated memory requests are completed before the Clocks a nd
Power Manager initiates the desired mode or sequence.
To ensure that CCLKCFG[TURBO] does not change when entering the frequency change
sequence, software must do a read-modify-write.
This is a read/wri te register. Ignore reads from reserved bit s. Write zeros to re served bits.
Table 3-23. Coprocessor 14 Clock and Power Management Summ a ry
Function Data in Rd Instruction
Read CCLKCFG MRC p14, 0, Rd, c6, c0, 0
Enter turbo mode TURBO = 1 MCR p14, 0, Rd, c6, c0, 0
Enter frequency change sequence FCS = 1
(Turbo mode bit may be set or
cleared in the same write) MCR p14, 0, Rd, c6, c0, 0
Enter idle mode M = 1 MCR p14, 0, Rd, c7, c0, 0
Enter sleep mode M = 3 MCR p14, 0, Rd, c7, c0, 0
Table 3-24. CCLKCFG Bit Definitions
CP14
Register 6 CCLKCFG Clocks and Power Manager
Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9876543210
reserved
FCS
TURBO
Reset 00000000000000000000000000000000
Bits Name Description
[31:2] — reserved
1FCS
Frequency Change Sequence
0 – Do not enter frequency change sequence
1 – Enter frequency change sequence
Cleared on hardware, watchdog, and GPIO reset and when sleep mode exits.
0TURBO
Turbo Mode
0 – Do not enter turbo mode/Exit turbo mode
1 – Enter turbo mode
Cleared on hardware, watchdog, and GPIO reset and when sleep mode exits.