
10-4
G2 PowerPC Core Reference Manual
For More Information On This Product,
Go to: www.freescale.com
MOTOROLA
Programmable Power Modes
Doze mode is characterized by the following features:
Most functional units disabled
Bus snooping and time base/decrementer still enabled
PLL running and locked to internal core_sysclk
To enter the doze mode, the following conditions must occur:
Set doze bit (HID0[8] = 1), MSR[POW] is set
G2 core enters doze mode after several processor clocks
To return to full-power mode, the following conditions must occur:
Assert internal core_int, core_smi, or core_mcp signals or decrementer interrupts
Hard reset or soft reset
Transition to full-power state occurs only after a few processor cycles
10.3.1.4 Nap Mode
The nap mode disables the G2 core except for the processor PLL and time
base/decrementer. The time base can be used to restore the core to a full-on state after a
specified period.
Because bus snooping is disabled for nap and sleep mode, a hardware handshake using the
quiesce request (core_qreq) and quiesce acknowledge (core_qack) signals are required to
maintain data coherency. The G2 core asserts the core_qreq signal to indicate that it is ready
to disable bus snooping, including all bus activity. Once the processor has entered a
quiescent state, it no longer snoops bus activity.
When the system logic has ensured that snooping is no longer necessary, it allows the
processor to enter the nap (or sleep) mode and causes the assertion of the G2 core core_qack
input signal for the duration of the nap mode period.
Nap mode is characterized by the following features:
Time base/decrementer still enabled
Most functional units disabled (including bus snooping)
PLL running and locked to internal core_sysclk
To enter the nap mode, the following conditions must occur:
Set nap bit (HID0[9] = 1), MSR[POW] bit is set
G2 core asserts core_qreq
System asserts core_qack
The processor core enters nap mode after several processor clocks
F
Freescale Semiconductor, Inc.
n
.