HD64F2149 Datasheet, PDF (767/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

24.11 Direct Transition
24.11.1 Overview of Direct Transition
There are three operating modes in which the CPU executes programs: high-speed mode, medium-
speed mode, and subactive mode. A transition between high-speed mode and subactive mode
without halting the program is called a direct transition. A direct transition can be carried out by
setting the DTON bit in LPWRCR to 1 and executing a SLEEP instruction. After the transition,
direct transition interrupt exception handling is started.
Direct Transition from High-Speed Mode to Subactive Mode: If a SLEEP instruction is
executed in high-speed mode while the SSBY bit in SBYCR, the LSON bit and DTON bit in
LPWRCR, and the PSS bit in TSCR (WDT1) are all set to 1, a transition is made to subactive
mode.
Direct Transition from Subactive Mode to High-Speed Mode: If a SLEEP instruction is
executed in subactive mode while the SSBY bit in SBYCR is set to 1, the LSON bit is cleared to 0
and the DTON bit is set to 1 in LPWRCR, and the PSS bit in TSCR (WDT1) is set to 1, after the
elapse of the time set in bits STS2 to STS0 in SBYCR, a transition is made to directly to high-
speed mode.
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