SH7721 datasheet(558/1524 Pages) RENESAS

558 / 1524 page

Section 13

Power-Down Modes

Rev. 3.00

Jan. 18, 2008

Page 496 of 1458

REJ09B0033-0300

13.8

Hardware Standby Mode

13.8.1

Transition to Hardware Standby Mode

This LSI enters hardware standby mode by driving the CA pin low. In hardware standby mode as

well as a standby mode entered by the SLEEP instruction, all modules stop other than the modules

that operate using the RTC clock.

Hardware standby mode differs from standby mode as follows:

1. Interrupts and manual reset cannot be accepted.

2. TMU does not operate.

3. RTC operates without power supply to the power supply pins other than that of RTC.

If the CA pin goes low, the operation differs according to the CPG status.

• During standby mode

Hardware standby mode is entered with the clock stopped.

Interrupts and manual reset cannot be accepted and TMU halts.

• During WDT operation while the standby mode is canceled by an interrupt

After standby mode is canceled and the CPU restarts operating, a transition to hardware

standby mode occurs.

• Sleep mode

After sleep mode is canceled and the CPU restarts operating, a transition to hardware standby

mode occurs.

Note that the CA pin must be brought low during hardware standby mode.

13.8.2

Canceling the Hardware Standby Mode

Hardware standby mode is canceled by power-on or reset. If the CA pin is pulled high while the

RESETP signal is low, clock oscillation starts. In this case, RESETP must be kept low until clock

oscillation has settled. If

RESETP is then pulled high, the CPU initiates the power-on reset

processing. If an interrupt or manual reset is input, correct operation cannot be guaranteed.

SH7721 Datasheet(PDF) 558 Page - Renesas Technology Corp