93
Bits 1 and 0—Subactive Mode Clock Select (SA1 and SA0): These bits select the CPU clock
rate (ø
W
/2, ø
W
/4, or ø
W
/8) in subactive mode. SA1 and SA0 cannot be modified in subactive mode.
Bit 1: SA1
Bit 0: SA0
Description
0
0
ø
W
/8
(initial value)
1
ø
W
/4
1
*
ø
W
/2
Note: * Don’t care
5.2
Sleep Mode
5.2.1
Transition to Sleep Mode
The system goes from active mode to sleep mode when a SLEEP instruction is executed while the
SSBY and LSON bits in system control register 1 (SYSCR1) are cleared to 0. In sleep mode CPU
operation is halted but the on-chip peripheral functions are operational. The CPU register contents
are retained.
5.2.2
Clearing Sleep Mode
Sleep mode is cleared by an interrupt (timer A, timer F, timer G, timer Y, IRQ
0
to IRQ
4
, WKP
0
to
WKP
7
, SCI1, SCI3, A/D converter) or by reset input.
Clearing by Interrupt: When an interrupt is requested, sleep mode is cleared and interrupt
exception handling starts. Operation resumes in active (high-speed) mode if MSON = 0 in
SYSCR2, or active (medium-speed) mode if MSON = 1. Sleep mode is not cleared if the I bit of
the condition code register (CCR) is set to 1 or the particular interrupt is disabled in the interrupt
enable register.
Clearing by Reset Input: When the
RES
pin goes low, or when a watchdog timer reset is
effected, the CPU goes into the reset state and sleep mode is cleared.