H8S2245 datasheet(606/818 Pages) RENESAS

606 / 818 page

Section 18 Power-Down Modes

Rev.3.00 Mar. 26, 2007 Page 564 of 772

REJ09B0355-0300

18.6

Software Standby Mode

18.6.1

Software Standby Mode

If a SLEEP instruction is executed when the SSBY bit in SBYCR is set to 1, software standby

mode is entered. In this mode, the CPU, on-chip supporting modules, and oscillator all stop.

However, the contents of the CPU's internal registers, RAM data, and the states of on-chip

supporting modules other than the SCI and A/D, and I/O ports, are retained. Whether the address

bus and bus control signals are placed in the high-impedance state or retain the output state can be

specified by the OPE bit in SBYCR.

In this mode the oscillator stops, and therefore power dissipation is significantly reduced.

18.6.2

Clearing Software Standby Mode

Software standby mode is cleared by an external interrupt (NMI pin, or pins

IRQ0 to IRQ2), or by

means of the

RES pin or STBY pin.

Clearing with an Interrupt

When an NMI or IRQ0 to IRQ2 interrupt request signal is input, clock oscillation starts, and after

the elapse of the time set in bits STS2 to STS0 in SBYCR, stable clocks are supplied to the entire

H8S/2245 Group chip, software standby mode is cleared, and interrupt exception handling is

started.

When clearing software standby mode with an IRQ0 to IRQ2 interrupt, set the corresponding

enable bit to 1 and ensure that no interrupt with a higher priority than interrupts IRQ0 to IRQ2 is

generated. Software standby mode cannot be cleared if the interrupt has been masked on the CPU

side or has been designated as a DTC activation source.

Clearing with the

RES

RES Pin

When the

RES pin is driven low, clock oscillation is started. At the same time as clock oscillation

starts, clocks are supplied to the entire H8S/2245 Group chip. Note that the

RES pin must be held

low until clock oscillation stabilizes. When the

RES pin goes high, the CPU begins reset exception

handling.

Clearing with the

STBY

STBY Pin

When the

STBY pin is driven low, a transition is made to hardware standby mode.

H8S2245 Datasheet(PDF) 606 Page - Renesas Technology Corp

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