Renesas Hitachi H8S/2191, Hardware Manual

Page: 113 / 1065

Rev. 2.0, 11/00, page 86 of 1037
4.10 Direct Transition
4.10.1 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.
(1) 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 TMA3 bit in TMA (Timer A) are all set to 1,
a transition is made to subactive mode.
(2) Direct Transition from Subactive Mode to High-Speed Mode/Medium-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 TMA3 bit
in TMA (Timer A) 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.
Note: * At the time of transition from subactive mode to high- or medium-speed mode, an
oscillation stabilization wait time is generated.