E202075_HD404889 Datasheet, PDF (55/202 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip LCD Circuit

HD404889/HD404899/HD404878/HD404868 Series
Active mode:
In active mode all functions operate. In this mode, the MCU operates on clocks generated by the OSC₁ and
OSC₂ oscillator circuits.
Standby mode:
In standby mode the oscillators continue to operate but clocks relating to instruction execution halt. As a
result, CPU operation stops, and registers, RAM, and the D port/R port set for output retain their state
immediately prior to entering standby mode. Interrupts, timers, the serial interface, and other peripheral
functions continue to operate.
Power consumption is lower than in active mode due to the halting of the CPU.
The MCU is switched to standby mode by executing the SBY instruction in active mode. Standby mode is
cleared by RESET input or an interrupt request. When standby mode is cleared by RESET input, an MCU
reset is performed. When standby mode is cleared by an interrupt request, the MCU enters active mode
and executes a instruction following the SBY instruction. After executing the instruction, if the interrupt
enable flag is set to 1, interrupt handling is executed; if the interrupt enable flag is cleared to 0, the interrupt
request is held pending and normal instruction execution is continued.
MCU operation flowchart is shown in figure 14.
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