HD6432351 datasheet(732/1025 Pages) RENESAS

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Section 20 Power-Down Modes

Rev. 3.00 Sep 15, 2006 page 698 of 988

REJ09B0330-0300

20.6.5

Usage Notes

I/O Port Status

In software standby mode, I/O port states are retained. If the OPE bit is set to 1, the address bus

and bus control signal output is also retained. Therefore, there is no reduction in current

dissipation for the output current when a high-level signal is output.

Current Dissipation during Oscillation Stabilization Wait Period

Current dissipation increases during the oscillation stabilization wait period.

Write Data Buffer Function

The write data buffer function and software standby mode cannot be used at the same time. When

the write data buffer function is used, the WDBE bit in BCRL should be cleared to 0 to cancel the

write data buffer function before entering software standby mode. Also check that external writes

have finished, by reading external addresses, etc., before executing a SLEEP instruction to enter

software standby mode. See section 6.9, Write Data Buffer Function, for details of the write data

buffer function.

20.7

Hardware Standby Mode

20.7.1

Hardware Standby Mode

When the

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

In hardware standby mode, all functions enter the reset state and stop operation, resulting in a

significant reduction in power dissipation. As long as the prescribed voltage is supplied, on-chip

RAM data is retained. I/O ports are set to the high-impedance state.

In order to retain on-chip RAM data, the RAME bit in SYSCR should be cleared to 0 before

driving the

STBY pin low.

Do not change the state of the mode pins (MD2 to MD0) while the H8S/2350 Group is in hardware

standby mode.

Hardware standby mode is cleared by means of the

STBY pin and the RES pin. When the STBY

pin is driven high while the

RES pin is low, the reset state is set and clock oscillation is started.

Ensure that the

RES pin is held low until the clock oscillator stabilizes (at least 8 ms—the

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