HD6433802H Datasheet, PDF (109/435 Pages) Hitachi Semiconductor – Single-Chip Microcomputer

1. Oscillation settling time (t_rc)
The time from the point at which the system clock oscillator oscillation waveform starts to change
when an interrupt is generated, until the amplitude of the oscillation waveform increases and the
oscillation frequency stabilizes.
2. Standby time
The time required for the CPU and peripheral functions to begin operating after the oscillation
waveform frequency and system clock have stabilized.
The standby time setting is selected with standby timer select bits 2 to 0 (STS2 to STS0) (bits 6 to
4 in system control register 1 (SYSCR1)).
Oscillation
waveform
(OSC2)
System clock
(ø)
Oscillation
settling time
Standby time
Operating
mode
Standby mode,
watch mode,
or subactive
mode
Oscillation settling standby time
Active (high-speed) mode or
active (medium-speed) mode
Interrupt accepted
Figure 4.12 Oscillation Settling Standby Time
When standby mode, watch mode, or subactive mode is cleared by an interrupt or reset, and a
transition is made to active (high-speed/medium-speed) mode, the oscillation waveform begins to
change at the point at which the interrupt is accepted. Therefore, when an oscillator element is
connected in standby mode, watch mode, or subactive mode, since the system clock oscillator is
halted, the time from the point at which this oscillation waveform starts to change until the
amplitude of the oscillation waveform increases and the oscillation frequency stabilizes—that is,
the oscillation settling time—is required.
91