Intel PXA255 Personal Computer User Manual


 
3-36 Intel® PXA255 Processor Developer’s Manual
Clocks and Power Manager
3.6.2 Clock Enable Register (CKEN)
CKEN, shown in Table 3-21, enables or disables the clocks to most of the peripheral units. For
lowest power consumption, the clock to any unit that is not being used must be disabled by writing
a zero to the appropriate bit.
This is a read/write register. Ignore reads from reserved bits. Write zeros to reserved bits.
Table 3-21. CKEN Bit Definitions (Sheet 1 of 2)
0x4130_0004 CKEN Clocks Manager
Bit
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
reserved
CKEN16
reserved
CKEN14
CKEN13
CKEN12
CKEN11
reserved
reserved
CKEN8
CKEN7
CKEN6
CKEN5
reserved
CKEN3
CKEN2
CKEN1
CKEN0
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 1 1 1 0 1 1 1 1 0 1 1 1 1
Bits Name Description
[31:17] reserved
16 CKEN16
LCD Unit Clock Enable
0 – Clock to the unit is disabled
1 – Clock to the unit is enabled.
Set by hardware and watchdog resets
15 reserved
14 CKEN14
I2C Unit Clock Enable
0 – Clock to the unit is disabled
1 – Clock to the unit is enabled.
Set by hardware and watchdog resets
13 CKEN13
FICP Unit Clock Enable
0 – Clock to the unit is disabled
1 – Clock to the unit is enabled.
These bits are set by hardware reset or watchdog reset
12 CKEN12
MMC Unit Clock Enable
0 – Clock to the unit is disabled
1 – Clock to the unit is enabled.
These bits are set by hardware reset or watchdog reset
11 CKEN11
USB Unit Clock Enable
0 – Clock to the unit is disabled
1 – Clock to the unit is enabled.
Set by hardware and watchdog resets
This bit must be set to allow the 48Mhz clock output on GP7 Alternate Function 1.
10 reserved
9CKEN9
NSSP Unit Clock Enable
0 – Clock to the unit is disabled
1 – Clock to the unit is enabled.
Set by hardware and watchdog resets