HD64F3687GHV Datasheet, PDF (139/566 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 6 Power-Down Modes
6.3 Operating Frequency in Active Mode
Operation in active mode is clocked at the frequency designated by the MA2, MA1, and MA0 bits
in SYSCR2. The operating frequency changes to the set frequency after SLEEP instruction
execution.
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
Rev. 3.00 Sep. 10, 2007 Page 105 of 528
REJ09B0216-0300