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MB95630H Series
3.5.5
Watch Mode
In watch mode, only the subclock, the sub-CR clock and the watch prescaler
operate. The CPU and the operating clock for peripheral functions are stopped
in this mode.
■ Operations in Watch Mode
In watch mode, while retaining the contents of registers and RAM existing at the point
immediately before the device transits to watch mode, the device stops all functions except the
watch prescaler, external interrupt and low-voltage detection reset.
In the case of hardware watchdog timer, if it is enabled in standby mode by the non-volatile
register function, in watch mode, the sub-CR clock does not stop and the hardware watchdog
timer continues its operation. For details, see "CHAPTER 26 NON-VOLATILE REGISTER
(NVR) INTERFACE".
● Transition to watch mode
If the clock mode monitor bits in the system clock control register (SYCC:SCM[2:0]) are
"0b000" or "0b100", writing "1" to the watch bit in the standby control register (STBC:TMD)
causes the device to transit to watch mode.
The device can transit to watch mode only when the clock mode is subclock mode or sub-CR
clock mode.
After the device transits to watch mode, if the pin state setting bit in the standby control
register (STBC:SPL) is "0", the states of the external pins are kept; if the SPL bit is "1", the
states of the external pins become high impedance (a pin is pulled up if the pull-up resistor
connection for that pin is selected in the pull-up register).
● Release from watch mode
The device is released from watch mode by a reset, a watch interrupt, or an external interrupt.
With the deep standby mode control bit (STBC2:DSTBYX) set to "0", even after a reset occurs
or an interrupt is generated by a peripheral function, the device transits to sleep mode until the
Flash recovery wait time elapses.
However, if a program is being executed on the RAM, no Flash recovery wait time occurs.
Note:
If the device is released from watch mode by an interrupt, a peripheral function having
transited to time-base timer mode during operation resumes operating from the point at
which it transited to time-base timer mode. Therefore, some settings of that peripheral
function, such as the initial interval time of the interval timer, become undefined. Initialize
that peripheral function if necessary after releasing the device from watch mode.
MN702-00009-1v0-E
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER 3 CLOCK CONTROLLER
3.5 Operations in Low Power Consumption
Mode (Standby Mode)
53
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