HD64F36049 datasheet(118/562 Pages) RENESAS

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Section 6 Power-Down Modes

Rev. 3.00 Mar. 15, 2006 Page 86 of 526

REJ09B0060-0300

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 + 16 × 8 tw = 3 tosc + 128 tw

(when the CPU operating clock of

osc → φw/8 is selected)

[Legend]

tosc:

OSC clock cycle time

tw:

Watch clock cycle time

tcyc:

System clock (

φ) cycle time

tsubcyc:

Subclock (

SUB) cycle time

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