Fujitsu F2MC-8L MB89620 Series Hardware Manual page 89

3.7 Standby Modes (Low-power Consumption)
3.7.2 Stop Mode
This section describes the operations of stop mode.
n Operation of Stop Mode
Changing to stop mode
l
Stop mode stops the source oscillation. All chip functions other than external interrupts stop
while maintaining all register and RAM contents at their values immediately before changing to
stop mode. Accordingly, data can be held with minimum power consumption.
Writing "1" to the stop bit in the standby control register (STBC: STP) changes the CPU to stop
mode. At this time, external pin states are held if the pin state specification bit (STBC: SPL) is
"0". If SPL is "1", external pins go to the high-impedance state. (Pins with a pull-up resistor
(optional) go to the "H" level)
If an interrupt request is generated when "1" is written to the STP bit, the write to the bit is
ignored, and the CPU continues the instruction execution without change to stop mode. (The
CPU does not assume stop mode even after completion of the interrupt processing.)
Prohibit interrupt request output from the timebase timer (TBTC: TBIE = "0") before changing to
stop mode as necessary.
l Wake-up from stop mode
A reset or an external interrupt wakes up CPU from stop mode.
If a reset occurs during stop mode on a product with power-on reset, the reset operation starts
after the oscillation stabilization delay time.
Products without power-on reset do not require for the oscillation stabilization delay time after a
reset in stop mode or at power-on.
The reset initializes pin states.
If an interrupt request with an interrupt level higher than "11" occurs from an external interrupt
circuit during stop mode, the CPU wakes up from stop mode, regardless of the interrupt enable
flag (CCR: I) and interrupt level bits (CCR: IL1, IL0) in the CPU. Only external interrupt requests
can occur during stop mode because peripheral functions are stopped.
After wake-up from stop mode, the normal interrupt operation is performed after the oscillation
stabilization delay time has passed. If the interrupt request is accepted, the CPU executes
interrupt processing. If the interrupt request is not accepted, the CPU continues execution from
the subsequent instruction following the instruction executed immediately before entering stop
mode.
Some peripheral functions restart from mid-operation when the CPU wakes up from stop mode
by an external interrupt. The first interval time from the interval timer function, for example, is
indeterminate. Therefore, initialize all peripheral functions after wake-up from stop mode.
Check: Only interrupt requests from external interrupt circuits can be used to wake up from stop mode by
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CHAPTER 3 CPU
an interrupt.
MB89620 series