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5. Power-Down Modes
Direct Transfer from Subactive Mode to Active (Medium-Speed) Mode: When a SLEEP
instruction is executed in subactive mode while the SSBY bit in SYSCR1 is set
to 1, the LSON bit in SYSCR1 is cleared to 0, the MSON bit in SYSCR2 is set to 1, the DTON bit
in SYSCR2 is set to 1, and TMA3 bit in TMA is set to 1, a transition is made directly to active
(medium-speed) mode via watch mode after the waiting time set in SYSCR1 bits STS2 to STS0
has elapsed.
5.8.2
Calculation of Direct Transfer Time before Transition
Time Required before Direct Transfer from Active (High-speed) Mode to Active (Medium-
Speed) Mode: A direct transfer is made 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, the MSON bit in SYSCR2 is set to 1, and the DTON bit in
SYSCR2 is set to 1. A direct transfer time, that is, the time from SLEEP instruction execution to
interrupt exception handling completion is calculated by expression (1) below.
Direct transfer time = (number of states for SLEEP instruction execution + number of
Example: Direct transfer time for the H8/3857 Group and H8/3854 Group
= (2 + 1) × 2tosc + 14 × 16tosc = 230 tosc
Legend:
tosc: OSC clock cycle time
tcyc: System clock (φ) cycle time
Time Required before Direct Transfer from Active (Medium-Speed) Mode to Active (High-
Speed) Mode: A direct transfer is made from active (medium-speed) mode to active (high-speed)
mode when a SLEEP instruction is executed in active (medium-speed) mode while the SSBY and
LSON bits in SYSCR1 are cleared to 0, the MSON bit in SYSCR2 is cleared to 0, and the DTON
bit in SYSCR2 is set to 1. A direct transfer time, that is, the time from SLEEP instruction
execution to interrupt exception handling completion is calculated by expression (2) below.
Direct transfer time = (number of states for SLEEP instruction execution + number of
Rev.3.00 Jul. 19, 2007 page 116 of 532
REJ09B0397-0300
states for internal processing) × tcyc before transition + number of
states for interrupt exception handling execution × tcyc after
transition
states for internal processing) × tcyc before transition + number of
states for interrupt exception handling execution × tcyc after
transition
...... (1)
...... (2)
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