104
5.3.2
Clearing Standby Mode
Standby mode is cleared by an interrupt (IRQ
1
or IRQ
0
), WKP
7
to WKP
0
or by input at the
RES
pin.
• Clearing by interrupt
When an interrupt is requested, the system clock pulse generator starts. After the time set in bits
STS2 to STS0 in SYSCR1 has elapsed, a stable system clock signal is supplied to the entire chip,
standby 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.
Standby mode is not cleared if the I bit of CCR is set to 1 or the particular interrupt is disabled in
the interrupt enable register.
• Clearing by
RES
input
When the
RES
pin goes low, the system clock pulse generator starts. After the pulse generator
output has stabilized, if the
RES
pin is driven high, the CPU starts reset exception handling. Since
system clock signals are supplied to the entire chip as soon as the system clock pulse generator
starts functioning, the
RES
pin should be kept at the low level until the pulse generator output
stabilizes.