
CLOCK GE NE R AT ING CIR CUIT
7721 Group User’s Manual
5–6
(1)
Termination by interrupt request occurrence
When terminating Stop mode by interrupt request occurrence, instructions are executed after a
certain time measured by the watchdog timer has passed.
When an interrupt request occurs, the oscillator starts oscillating. Simultaneously, supply of clock
φ
1
, f
2
to f
512
starts.
The watchdog timer starts counting owing to the oscillation start. The watchdog timer counts f
32
regardless of the watchdog timer frequency select bit’s (bit 0 at address 61
16
) contents.
When the watchdog timer’s MSB becomes “0,” supply of
φ
CPU
and
φ
starts. At the same time, the
watchdog timer’s count source returns to f
32
or f
512
that is selected by the watchdog timer frequency
select bit.
The interrupt request which occurred in
is accepted.
Table 5.3.2 lists the interrupts used to terminate Stop mode.
Table 5.3.2 Interrupts used to terminate Stop mode
Interrupt
____
i
interrupt (i = 0 to 2)
Timer Ai interrupt (i = 2 to 4)
Timer Bi interrupt (i = 0, 1)
UARTi transmit interrupt (i = 0, 1)
UARTi receive interrupt (i = 0, 1)
Notes 1:
Since the oscillator has stopped oscillating, interrupts not listed above cannot be used. Also, even
the interrupts listed above cannot be used when the above conditions are not satisfied. The
A-D converter does not operate, also.
2:
When multiple interrupts listed above are enabled, Stop mode is terminated by the interrupt
request which occurs first.
3:
Refer to
“CHAPTER 7. INTERRUPTS”
and the description of each internal peripheral device for
details about each interrupt.
5.3 Stop mode
Conditions for using each function to generate interrupt request
In event counter mode
When external clock is selected
Before executing the
STP
instruction, interrupts used to terminate Stop mode must be enabled.
In addition, the interrupt priority level of the interrupt used to terminate Stop mode must be higher
than the processor interrupt priority level (IPL) of the routine where the
STP
instruction is executed.
When multiple interrupts in Table 5.3.2 are enabled, Stop mode is terminated by the first interrupt
request.
There is a possibility that any of all interrupt requests occurs after the oscillation starts in
and until
supply of
φ
CPU
and
φ
starts in
. The interrupt requests which occur during this period are accepted
in order of priority after the watchdog timer’s MSB becomes “0.”
For interrupts not to be accepted, set their interrupt priority levels to level 0 (interrupt disabled)
before executing the
STP
instruction.