HD64F2149 Datasheet, PDF (762/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

24.7 Hardware Standby Mode
24.7.1 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 (MD1 and MD0) while the chip 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 oscillation settles (at least 8 ms—the oscillation
settling 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.
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