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ManualsBrandsRENESAS ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller LQFP 64 (10x10) 16-Bit 24 MHz I/O number 37
671672673674675676677678679680
Section 20 Power-Down Modes
Rev.7.00 Dec. 24, 2008 Page 624 of 698
REJ09B0074-0700
20.7 Watch Mode
20.7.1 Transition to Watch Mode
CPU operation makes a transition to watch mode when the SLEEP instruction is executed in high-
speed mode or subactive mode with SBYCR SSBY=1, LPWRCR DTON = 0, and TCSR_1
PSS = 1.
In watch mode, the CPU is stopped and peripheral modules other than RTC are also stopped. The
contents of the CPU’s internal registers, the data in internal RAM, and the statuses of the internal
peripheral modules (excluding the A/D converter) and I/O ports are retained. To make a transition
to watch mode, bits SCK2 to SCK0 in SCKCR must be set to 0.
20.7.2 Exiting Watch Mode
Watch mode is exited by any interrupt (WOVI interrupt, NMI pin, or IRQ0, to IRQ7), or signals at
the RES, MRES*, or STBY pin.
• Exiting Watch Mode by Interrupts
When an interrupt occurs, watch mode is exited and a transition is made to high-speed mode or
medium-speed mode when the LPWRCR LSON bit = 0 or to subactive mode when the LSON
bit = 1. When a transition is made to high-speed mode, a stable clock is supplied to all LSI
circuits and interrupt exception processing starts after the time set in SBYCR STS2 to STS0
has elapsed. In case of IRQ0, to IRQ7 interrupts, no transition is made from watch mode if the
corresponding enable bit/pin function switching bit has been cleared to 0, and, in the case of
interrupts from the internal peripheral modules, the interrupt enable register has been set to
disable the reception of that interrupt, or is masked by the CPU.
See section 20.4.3, Setting Oscillation Stablization Time after Clearing Software Standby
Mode, for how to set the oscillation settling time when making a transition from watch mode to
high-speed mode.
• Exiting Watch Mode by RES or MRES* pin
For exiting watch mode by the RES or MRES* pin, see section 20.4.2, Clearing Software
Standby Mode.
• Exiting Watch Mode by STBY pin
When the STBY pin level is driven low, a transition is made to hardware standby mode.
Note: * Supported only by the H8S/2218 Group.