
Phase-Locked Loop and Power Control
3-8
MC68328 DRAGONBALL PROCESSOR USER’S MANUAL
MOTOROLA
the clock is always off. Set the WIDTH to 0 when the CPU should be disabled for extended
time periods, but it can be awakened without waiting for the PLL to re-acquire lock.
These bits are not affected by the PC EN bit. When an interrupt disables the power con-
troller, these bits are not changed. Users should re-enable the power controller that ser-
vices the interrupt.
3.4.3 Operation
This section describes how to use the power controller.
3.4.3.1 NORMAL OPERATION.
When the MC68328 processor begins operation after
reset, the power controller is disabled and the MC68EC000 clock runs continuously. To
reduce the power consumed by the MC68EC000, the power controller is enabled when the
PC EN bit is set. The value in the WIDTH register determines the duty cycle of the clock that
is applied to the MC68EC000. If an interrupt is received, the power controller is automatically
disabled. It is up to the interrupt-service routine to re-enable the power controller.
3.4.3.2 DOZE OPERATION.
The MC68EC000 clock can be disabled for extended periods
by setting the WIDTH register to 00000. The MC68EC000 clock is enabled when it receives
an interrupt. At the end of the service routine, the power controller can be re-enabled, putting
the MC68EC000 back into DOZE mode. Once the MC68EC000 clock is disabled, only an
interrupt or hardware reset can re-enable it. For various MC68EC000 resource require-
ments, users can program the duty-cycle register for burst-duty cycles of any value between
0/31 and 31/31. This effectively provides a variable clock frequency (and power dissipation)
of between 0% and 100% of the system clock frequency in 3% incremental steps.
3.4.3.3 SLEEP OPERATION.
The PLL is disabled in the SLEEP mode. Only the 32 kHz
clock continuously operates to keep the real-time clock operational. Wakeup events can
activate the PLL and the system clock will begin to operate within 2 msec.
Summary of Contents for DragonBall MC68328
Page 5: ...vi MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 25: ...Overview 1 14 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 45: ...System Integration Module 2 20 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 103: ...Parallel Ports 7 16 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 117: ...UART 8 14 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...
Page 127: ...SPI Master 10 6 MC68328 DRAGONBALL PROCESSOR USER S MANUAL MOTOROLA ...