HD64F38602R Datasheet, PDF (123/552 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

Section 5 Power-Down Modes
5.3 Direct Transition
The CPU can execute programs in two modes: active and subactive modes. A direct transition is
made between these two modes without stopping program execution. A direct transition can also
be made when the operating clock is changed in active and subactive modes. The transition is
made via the sleep or watch mode, by setting the DTON bit in SYSCR2 to 1 to execute a SLEEP
instruction. After the mode transition, direct transition interrupt exception handling starts.
Note that if a direct transition is attempted while the I bit in CCR is 1, the transition is made to the
sleep or watch mode, though not returning from the mode.
5.3.1 Direct Transition from Active (High-Speed) Mode to Active (Medium-Speed) Mode
When a SLEEP instruction is executed in active (high-speed) mode while the SSBY and LSON
bits in SYSCR1 are cleared to 0 and the MSON and DTON bits in SYSCR2 are set to 1, a
transition is made to active (medium-speed) mode via sleep mode.
The time from the start of SLEEP instruction execution to the end of interrupt exception handling
(the direct transition time) is calculated by equation (1).
Direct transition time = {(Number of SLEEP instruction execution states) + (Number of internal
processing states)} × (tcyc before transition) + (Number of interrupt
exception handling execution states) × (tcyc after transition)…………(1)
Example: When φosc/8 is selected as the CPU operating clock after the transition
Direct transition time = (2 + 1) × 1tosc + 14 × 8tosc = 115tosc
For the legend of symbols used above, refer to section 21, Electrical Characteristics.
Rev. 3.00 May 15, 2007 Page 91 of 516
REJ09B0152-0300