Fujitsu MB90480 Series Hardware Manual page 160

CHAPTER 6 LOW-POWER CONSUMPTION MODE
❍ Return by interrupt
The watch mode is canceled by the low-power consumption control circuit if an interrupt request
whose interrupt level is higher than 7 (other than IL2, IL1, and IL0=111
register (ICR)) is generated in a peripheral circuit, etc., in the watch mode. The mode
immediately changes to the sub-clock mode. After the change to the sub-clock mode, interrupts
are processed with the same method as for ordinary interrupt processing. If interrupts are
accepted by setting the I-flag of the condition code register (CCR), interrupt level mask register
(ILM), or the interrupt control register (ICR), then the CPU executes the interrupts. If an interrupt
cannot be accepted, the CPU continues processing beginning from an instruction next to the
instruction that was processed before the watch mode was set.
Note:
When executing an interrupt, an instruction next to the instruction specifying the watch mode is
normally executed first before an interrupt request is processed. If a change to the watch mode
occurs at the same time as an external bus hold request is received, an interrupt may be executed
first before the next instruction is executed.
Figure 6.5-2 illustrates the cancel operation of the watch mode.
Figure 6.5-2 Cancel operation of watch mode (external reset)
RST pin
Watch mode
Main clock
PLL clock
Sub clock
CPU clock
CPU operation
138
Oscillation stabilization wait
Not operating Not operating
Oscillating
Not operating
Not operating
Reset cancel
Watch mode cancel
of the interrupt control
B
During oscillation
Main clock
Processing
Sequence for resetting