HD64F3670 Datasheet, PDF (96/305 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

6.3 Operating Frequency in the Active Mode
Operation in the active mode is clocked at the frequency designated by the MA2, to MA0 bits in
SYSCR2. The operating frequency changes to the set frequency after SLEEP instruction
execution.
6.4 Direct Transition
The CPU can execute programs in active mode.The operating freuncy can be changed by making
a transition directly from active mode to active mode. A direct transition can be made by
executing a SLEEP instruction while the DTON bit in SYSCR2 is set to 1. The direct transition
also enables operating frequency modification in the active mode. After the mode transition, direct
transition interrupt exception handling starts.
If the direct transition interrupt is disabled in interrupt enable register 1, a transition is made
instead to the sleep mode. Note that if a direct transition is attempted while the I bit in CCR is set
to 1, the sleep mode will be entered, and the resulting mode cannot be cleared by means of an
interrupt.
6.5 Module Standby Function
The module-standby function can be set to any peripheral module. In the module standby mode,
the clock supply to modules stops to enter the power-down mode. The module standby mode
enables each on-chip peripheral module to enter the standby state by setting a bit that corresponds
to each module in MSTCR1 and MSTCR2 to 1 and cancels the mode by clearing the bit to 0.
Rev. 1.0, 03/01, page 72 of 280