Datasheet

Section 6 Power-Down Modes
Rev.5.00 Nov. 02, 2005 Page 86 of 500
REJ09B0027-0500
6.4 Direct Transition
The CPU can execute programs in two modes: active and subactive modes. A direct transition is a
transition between these two modes without stopping program execution. 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 or subactive 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 or subsleep mode. Note that if a direct transition is attempted while the I bit in
CCR is set to 1, sleep or subsleep mode will be entered, and the resulting mode cannot be cleared
by means of an interrupt.
6.4.1 Direct Transition from Active Mode to Subactive 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 states) ×
(tsubcyc after transition) (1)
Example
Direct transition time = (2 + 1) × tosc + 14 × 8tw = 3tosc + 112tw
(when the CPU operating clock of φ
osc
→ φ
w
/8 is selected)
Legend
tosc: OSC clock cycle time
tw: Watch clock cycle time
tcyc: System clock (φ) cycle time
tsubcyc: Subclock (φ
SUB
) cycle time
6.4.2 Direct Transition from Subactive Mode to Active 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 (2).
Direct transition time = {(number of SLEEP instruction execution states) + (number of internal
processing states)} × (tsubcyc before transition) + {(waiting time set in bits STS2 to STS0) +
(number of interrupt exception handling states)} × (tcyc after transition) (2)