Rev. 6.00, 08/04, page 131 of 628
5.4
Watch Mode
5.4.1
Transition to Watch Mode
The system goes from active or subactive mode to watch mode when a SLEEP instruction is
executed while the SSBY bit in SYSCR1 is set to 1 and bit TMA3 in TMA is set to 1.
In watch mode, operation of on-chip peripheral modules is halted except for timer A, timer F,
timer G, AEC and the LCD controller/driver (for which operation or halting can be set) is halted.
As long as a minimum required voltage is applied, the contents of CPU registers, the on-chip
RAM and some registers of the on-chip peripheral modules, are retained. I/O ports keep the same
states as before the transition.
5.4.2
Clearing Watch Mode
Watch mode is cleared by an interrupt (timer A, timer F, timer G, IRQ0, or WKP7 to WKP0) or
by input at the
RES
pin.
•
Clearing by interrupt
When watch mode is cleared by interrupt, the mode to which a transition is made depends on
the settings of LSON in SYSCR1 and MSON in SYSCR2. If both LSON and MSON are
cleared to 0, transition is to active (high-speed) mode; if LSON = 0 and MSON = 1, transition
is to active (medium-speed) mode; if LSON = 1, transition is to subactive mode. When the
transition is to active mode, after the time set in SYSCR1 bits STS2 to STS0 has elapsed, a
stable clock signal is supplied to the entire chip, watch mode is cleared, and interrupt exception
handling starts. Watch 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
Clearing by
RES
pin is the same as for standby mode; see 2. Clearing by
RES
pin in section
5.3.2, Clearing Standby Mode.
5.4.3
Oscillator StabilizationTime after Watch Mode is Cleared
The wait time is the same as for standby mode; see section 5.3.3, Oscillator Stabilization Time
after Standby Mode is Cleared.
5.4.4
Notes on External Input Signal Changes before/after Watch Mode
See section 5.3.5, Notes on External Input Signal Changes before/after Standby Mode.
Summary of Contents for H8/38024 Series
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