MPC555
/
MPC556
CLOCKS AND POWER CONTROL
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
8-17
decrementer exception is only three to four clock cycles of maximum system frequen-
cy. In 40-MHz systems, this wake-up requires 75 to 100 ns. The asynchronous wake-
up interrupt from the interrupt controller is level sensitive one. It will therefore be ne-
gated only after the reset of interrupt cause in the interrupt controller.
The timers (RTC, PIT, time base, or decrementer) interrupts indication set status bits
in the PLPRCR (TMIST). The clock module considers this interrupt to be pending
asynchronous interrupt as long as the TMIST is set. The TMIST status bit should be
cleared before entering any low-power mode.
summarizes wake-up operation for each of the low-power modes.
8.8.3.1 Exiting from Normal-Low Mode
In normal mode (as well as doze mode), if the PLPRCR[CSRC] bit is set, the system
toggles between low frequency (defined by PLPRCR[DFNL]) and high frequency (de-
fined by PLPRCR[DFNH]. The system switches from normal-low mode to normal-high
mode if either of the following conditions is met:
• An interrupt is pending from the interrupt controller; or
• The MSR[POW] bit is cleared (power management is disabled).
When neither of these conditions are met, the PLPRCR[CSRC] bit is set, and the asyn-
chronous interrupt status bits are reset, the system returns to normal-low mode.
8.8.3.2 Exiting from Doze Mode
The system changes from doze mode to normal-high mode whenever an interrupt is
pending from the interrupt controller.
8.8.3.3 Exiting from Deep-Sleep Mode
The system switches from deep-sleep mode to normal-high mode if any of the follow-
ing conditions is met:
Table 8-6 Power Mode Wake-Up Operation
Operation Mode
Wake-up
Method
Return Time from Wake-up
Event to Normal-High
Normal-low (“gear”)
Software
or
Interrupt
Asynchronous interrupts:
3-4 maximum system cycles
Synchronous interrupts:
3-4 actual system cycles
Doze-high
Interrupt
Doze-low
Interrupt
Sleep
Interrupt
3-4 maximum system clocks
Deep-sleep
Interrupt
< 500 Oscillator Cycles
125 µsec – 4 MHz
25 µsec – 20 MHz
Power-down
Interrupt
< 500 oscillator power
supply wake-up
V
DDSRAM
External
Power-on sequence
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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