
71
3.7 Standby Mode (Low-Power Consumption Mode)
3.7.3
Stop Mode
This section describes the stop mode.
s Operations Relating to Stop Mode
r Transition to stop mode
In stop mode, the source oscillation is stopped. Most functions stop storing data in the registers
and RAM used immediately before transition to stop mode.
The clock circuit stops oscillating, the peripheral functions and CPU stop operating, but the
external interrupt circuit continues to operate.
Writing 1 to the stop bit in the standby control register (STBC: STP) causes a transition to stop
mode. At that time, if the terminal state setting bit (STBC: SPL) is 0, the states of the external
terminals are maintained. If the terminal state setting bit is 1, the states of the external terminals
are set to Hi-Z (the states of terminals for which a pull-up resistor is specified in the pull-up
setting resistor are set to level H).
An attempt to write 1 into the STP bit while an interrupt request is being generated fails,
transition to stop mode cannot made, and instructions are processed continuously. (Even after
the interrupt is processed completely, transition to stop mode is not made.)
For a transition to stop mode, prohibit the time base timer interrupt request output (TBTC: TBIE
= 0) when necessary.
r Cancellation of stop mode
Stop mode is canceled by a reset or external interrupt.
When a reset occurs in stop mode, the reset operation is performed after oscillation stabilization
wait time.
Terminal states are initialized by the reset operation.
When an interrupt request with an interrupt level higher than 11B is generated in an external
interrupt circuit in stop mode, stop mode is cancelled regardless of the CPU interrupt enable flag
(CCR: I) or interrupt bit level (CCR: IL1 and IL0).
When stop mode is cancelled and oscillation stabilization wait time has expired, a normal
interrupt operation is performed .
Then, if interrupts are acceptable, interrupt processing is
performed. Otherwise, an instruction following the instruction immediately before transition to
stop mode is managed.
When an external interrupt cancels stop mode, part of the peripheral functions are restarted with
data stored before the beginning of sleep mode. Therefore, the initial interval of the interval
timer and other similar settings are rendered unknown.
The peripheral functions must be
initialized after returning from stop mode.
Caution:
Among interrupts, only an interrupt request from the external interrupt circuit cancels the stop
mode.