HD6432345 Datasheet, PDF (638/907 Pages) Hitachi Semiconductor – H8S/2345 F-ZTAT Hardware Manual

19.7 Hardware Standby Mode
19.7.1 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/2345 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
state.
19.7.2 Hardware Standby Mode Timing
Figure 19.3 shows an example of hardware standby mode timing.
When the STBY pin is driven low after the RES pin has been driven low, a transition is made to
hardware standby mode. Hardware standby mode is cleared by driving the STBY pin high,
waiting for the oscillation stabilization time, then changing the RES pin from low to high.
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