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CHAPTER 5 LOW POWER CONSUMPTION MODE
MB90560 series
5.8
Notes on Using Low Power Consumption Mode
Note the following six items to use low power consumption mode:
Switching to standby mode and interrupts
Release of standby mode by an interrupt
Setting of standby mode
Release of stop mode
Release of timebase timer mode
Oscillation stabilization wait time
I
Notes on standby mode
G
Switching to standby mode and interrupts
During an interrupt request to the CPU from a peripheral function, the CPU ignores the STP and
SLP bits of the low power consumption mode control register (LPMCR) even though “1” has
been written to these bits. Thus, switching to any standby mode is disabled (even after
processing the interrupt is completed, there is no switch to standby mode). If the interrupt level is
7 or a higher priority, this action does not depend on whether the interrupt request is accepted
by the CPU.
However, during execution of interrupt processing by the CPU, if the interrupt request flag for the
interrupt is cleared and no other interrupt requests have been issued, switching to standby mode
can be done.
G
Release of standby mode caused by an interrupt
If an interrupt request of interrupt level 7 or a higher priority is issued from a peripheral function
during the sleep, timebase timer, or stop modes, the standby mode is released. This action does
not depend on whether the CPU accepts that interrupt.
After the release of standby mode, normal interrupt processing is performed. The CPU branches
to the interrupt handling routine provided that the priority of the interrupt request indicated by the
interrupt level setting bits (IL2, IL1, and IL0 of ICR) is higher than the interrupt level mask
register (ILM); and the interrupt enable flag (I) of the condition code register (CCR) is set to “1”
(enabled). If the interrupt is not accepted, the CPU starts the execution with the instruction that
follows the instruction in which switching to standby mode was specified.
When interrupt processing is executed normally, the CPU first executes the instruction that
follows the instruction in which switching to standby mode was specified. The CPU then
proceeds to interrupt processing. Depending on the condition when switching to standby mode
was performed, however, the CPU may proceed to interrupt processing before executing the
next instruction.
If the CPU should not branch to the interrupt processing routine immediately on return to normal
mode from standby mode, action must be taken to disable interrupts before standby mode is set.
G
Setting of standby mode
When “1” is written to the STP bit and SLP bit of LPMCR at the same time, switching to standby
mode is performed. If the MCS bit of the clock selection register (CKSCR) is “0”, switching to
timebase timer mode is performed; if this bit is 1, switching to stop mode is performed.