HD64F3670 Datasheet, PDF (97/323 Pages) Renesas Technology Corp – Hitachi Single-Chip Microcomputer

6.3 Operating Frequency in Active Mode
Operation in 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 frequency 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 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 sleep mode. Note that if a direct transition is attempted while the I bit in CCR is set to 1,
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 module standby mode, the
clock supply to modules stops to enter the power-down mode. 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. 2.0, 03/02, page 73 of 298