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CHAPTER 3 CPU
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Precaution in Setting the Standby Mode
To set the standby mode using the standby control register (STBC), follow Table 3.8-5 "Low
Power Consumption Settings by the Standby Control Register (STBC)". The priority order when
"1" is written into these bits is the stop mode, watch mode, and sleep mode. However, it is
preferable to set "1" to one bit at a time.
Do not make a transition to the stop mode, sleep mode, and watch mode just after switching
from the subclock mode to the main clock mode (SYCC: SCS=0 --> 1). Make a transition to
these modes after checking that the clock monitor bit (SYCC: SCM) of the system control
register is "1".
However, the content written into the clock bit (TMD) is ignored during operation in main clock
mode.
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Oscillation Stabilization Wait Time
Since the oscillator for oscillation is stopped in stop mode for both the main clock mode and
subclock mode, it is necessary to take the oscillation stabilization wait time after the oscillator in
each mode starts operation.
As the oscillation stabilization wait time in main clock mode, take the oscillation stabilization wait
time of the main clock created by the timebase timer (Select one from three different kinds of
wait time). As the oscillation stabilization wait time in subclock mode, take the oscillation
stabilization wait time of the subclock created by the watch prescaler.
In main clock mode, if the selected interval time of the timebase timer is shorter than the
oscillation stabilization wait time, an interval timer interrupt request may occur during oscillation
stabilization wait time. Before making a transition to the stop mode in main clock mode, prohibit
(TBTC: TBIE=0) the interrupt request output of the timebase timer if necessary.
Likewise, a watch interrupt request may occur depending on the selected interval time of the
watch prescaler. Before making a transition to the stop mode in subclock mode, prohibit
(WPCR: WIE=0) the watch interrupt request output of the watch prescaler if necessary.
Table 3.8-5 Low Power Consumption Settings by the Standby Control Register (STBC)
STBC register
Mode
STP (bit 7)
SLP (bit 6)
TMD (bit 3)
0
0
0
Normal
0
0
1
Clock
0
1
0
Watch
1
0
0
Stop