MPC555
/
MPC556
CLOCKS AND POWER CONTROL
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
8-16
8.8.2 Power Mode Descriptions
describes the power consumption, clock frequency, and chip functionality
for each power mode.
8.8.3 Exiting from Low-Power Modes
Exiting from low-power modes occurs through an asynchronous interrupt or a synchro-
nous interrupt generated by the memory controller. Any enabled asynchronous inter-
rupt clears the LPM bits but does not change the PLPRCR[CSRC] bit.
The exit from normal-low, doze-high, and low modes and sleep mode to normal-high
mode is accomplished with the asynchronous interrupt. The sources of the asynchro-
nous interrupt are:
• Asynchronous wake-up interrupt from the interrupt controller
• RTC, PIT, or time base interrupts (if enabled)
• Decrementer exception
The system response to asynchronous interrupts is fast. The wake-up time from nor-
mal-low, doze-high, doze-low, and sleep mode due to an asynchronous interrupt or
Table 8-4 Power Mode Control Bit Descriptions
Power Mode
LPM[0:1]
CSRC
TEXPS
Normal-high
00
0
X
Normal-low (“gear”)
00
1
X
Doze-high
01
0
X
Doze-low
01
1
X
Sleep 10
X
X
Deep-sleep 11
X
1
Power-down
11
X
0
Table 8-5 Power Mode Descriptions
Operation Mode
SPLL
Clocks
Functionality
Normal-high
Active
Full frequency ÷
2
DFNH
Full functions not in use
are shut off
Normal-low (“gear”)
Active
Full frequency ÷
2
DFNL+1
Doze-high
Active
Full frequency ÷
2
DFNH
Enabled: RTC, PIT,
TB and DEC,
memory controller
Disabled: extended
core
(RCPU, BBC, FPU)
Doze-low
Active
Full frequency ÷
2
DFNL+1
Sleep
Active
Not active
Enabled: RTC, PIT, TB
and DEC
Deep-sleep
Not active
Not active
Power-down
Not active
Not active
VDDSRAM
Not active
Not active
SRAM’s data
retention
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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