Renesas H8/38024 Series, Руководство по оборудованию

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Rev. 6.00, 08/04, page 126 of 628
5.3 Standby Mode
5.3.1 Transition to Standby Mode
The system goes from active mode to standby mode when a SLEEP instruction is executed while
the SSBY bit in SYSCR1 is set to 1, the LSON bit in SYSCR1 is cleared to 0, and bit TMA3 in
TMA is cleared to 0. In standby mode the clock pulse generator stops, so the CPU and on-chip
peripheral modules stop functioning, but as long as the rated voltage is supplied, the contents of
CPU registers, on-chip RAM, and some on-chip peripheral module registers are retained. On-chip
RAM contents will be further retained down to a minimum RAM data retention voltage. The I/O
ports go to the high-impedance state. Port 5 of the HD64F38024 retains the previous pin state.
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.