68HC05P4A_1 Datasheet, PDF (35/83 Pages) Freescale Semiconductor, Inc – SPECIFICATION (General Release)

Freescale Semiconductor, Inc.
GENERAL RELEASE SPECIFICATION
6.1.2 Halt Mode
Execution of the STOP instruction with the conversion to halt places the MCU in
this low-power mode. Halt mode consumes the same amount of power as wait
mode. (Both halt and wait modes consume more power than stop mode.)
In halt mode the PH2 clock is halted, suspending all processor and internal bus
activity. Internal timer clocks remain active, permitting interrupts to be generated
from the 16-bit timer or a reset to be generated from the COP watchdog timer.
Execution of the STOP instruction automatically clears the I bit in the condition
code register enabling the IRQ external interrupt. All other registers, memory, and
input/output lines remain in their previous states.
If the 16-bit timer interrupt is enabled, the processor will exit the halt mode and
resume normal operation. The halt mode can also be exited when an IRQ external
interrupt or external RESET occurs. When exiting the halt mode, the PH2 clock
will resume after a delay of one to 4064 PH2 clock cycles. This varied delay time
is the result of the halt mode exit circuitry testing the oscillator stabilization delay
timer (a feature of the stop mode), which has been free-running (a feature of the
wait mode).
NOTE
The halt mode is not intended for normal use. This feature is
provided to keep the COP watchdog timer active in the event a
STOP instruction is inadvertently executed.
6.2 WAIT Instruction
The WAIT instruction places the MCU in a low-power mode, which consumes
more power than the stop mode. In wait mode, the PH2 clock is halted,
6-2
Rev. 2.0
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