Fujitsu F2MC-8L Series Hardware Manual page 106

Some peripheral functions restart from mid-operation when the CPU wakes up from stop mode
by an external interrupt. Accordingly, the first interval time for the interval timer function, for
example, becomes indeterminate. Therefore, initialize all peripheral functions after wake-up
from stop mode.
Check:
Only interrupt requests from external interrupt circuits can be used for the wake-up from stop
mode by an interrupt.
3.7 Standby Modes (Low-power Consumption)
79