HD404618 Datasheet, PDF (27/89 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404618 Series
Active Mode: The MCU operates according to the clock generated by the system oscillators OSC₁ and
OSC₂.
Standby Mode: The MCU enters standby mode when the SBY instruction is executed from active mode.
In this mode, the oscillators, interrupts, timer/counters, and serial interface continue to operate, but all
instruction execution-related clocks stop. The stopping of these clocks stops the CPU, retaining all RAM
and register contents and maintaining the current I/O pin status.
Standby mode is terminated by a RESET input or an interrupt request. If it is terminated by RESET input,
the MCU is reset as well. After an interrupt request, the MCU enters active mode and resumes, executing
the next instruction after the SBY instruction. If the interrupt enable flag is 1, that interrupt is then
processed; if it is 0, the interrupt request is left pending and normal instruction execution continues. A
flowchart of operation in standby mode is shown in figure 11.
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