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Rev. 1.00, 05/04, page 471 of 544
20.4 Sleep Mode
The CPU makes a transition to sleep mode if the SLEEP instruction is executed when the SSBY
bit in SBYCR is cleared to 0 and the LSON bit in LPWRCR is cleared to 0. In sleep mode, CPU
operation stops but the peripheral modules do not stop. The contents of the CPU's internal
registers are retained.
Sleep mode is exited by any interrupt, the RES pin, or the STBY pin.
When an interrupt occurs, sleep mode is exited and interrupt exception handling starts. Sleep mode
is not exited if the interrupt is disabled, or interrupts other than NMI are masked by the CPU.
Setting the RES pin level low cancels sleep mode and selects the reset state. After the oscillation
stabilization time has passed, driving the RES pin high causes the CPU to start reset exception
handling.
When the STBY pin level is driven low, sleep mode is cancelled and a transition is made to
hardware standby mode.
20.5 Software Standby Mode
The CPU makes a transition to software standby mode when the SLEEP instruction is executed
while the SSBY bit in SBYCR is set to 1, the LSON bit in LPWRCR is cleared to 0, and the PSS
bit in TCSR (WDT_1) is cleared to 0.
In software standby mode, the CPU, on-chip peripheral modules, and clock pulse generator all
stop. However, the contents of the CPU's internal registers, on-chip RAM data, I/O ports, and the
states of on-chip peripheral modules other than the SCI and PWM, are retained as long as the
prescribed voltage is supplied.
Software standby mode is cleared by an external interrupt (NMI, IRQ0 to IRQ2, IRQ6, or IRQ7),
the RES pin input, or STBY pin input.
When an external interrupt request signal is input, system clock oscillation starts, and after the
elapse of the time set in bits STS2 to STS0 in SBYCR, software standby mode is cleared, and
interrupt exception handling is started. When clearing software standby mode with an IRQ0 to
IRQ2, IRQ6, or IRQ7 interrupt, set the corresponding enable bit to 1 and ensure that no interrupt
with a higher priority than interrupts IRQ0 to IRQ2, IRQ6, and IRQ7 is generated. Software
standby mode cannot be cleared if an interrupt enable bit corresponding to an IRQ0 to IRQ2,
IRQ6, or IRQ7 interrupt is cleared to 0 or if the interrupt has been masked on the CPU side.