Hitachi H8S/2633 Hardware Manual page 886

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 7.9, Write Data Buffer

Function, for details of the write data buffer function.

Hardware Standby Mode

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/2633 Series 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

oscillation stabilization time—when using a crystal oscillator). When the RES pin is subsequently

driven high, a transition is made to the program execution state via the reset exception handling