HD6433802H Datasheet, PDF (108/435 Pages) Hitachi Semiconductor – Single-Chip Microcomputer

4.5 Note on Oscillators
Oscillator characteristics are closely related to board design and should be carefully evaluated by
the user in mask ROM and ZTAT™ versions, referring to the examples shown in this section.
Oscillator circuit constants will differ depending on the oscillator element, stray capacitance in its
interconnecting circuit, and other factors. Suitable constants should be determined in consultation
with the oscillator element manufacturer. Design the circuit so that the oscillator element never
receives voltages exceeding its maximum rating.
PB3
X1
X2
Vss
OSC2
OSC1
TEST
(Vss)
Figure 4.11 Example of Crystal and Ceramic Oscillator Element Arrangement
4.5.1 Definition of Oscillation Settling Standby Time
Figure 4.12 shows the oscillation waveform (OSC2), system clock (ø), and microcomputer
operating mode when a transition is made from standby mode, watch mode, or subactive mode, to
active (high-speed/medium-speed) mode, with an oscillator element connected to the system clock
oscillator.
As shown in figure 4.12, as the system clock oscillator is halted in standby mode, watch mode,
and subactive mode, when a transition is made to active (high-speed/medium-speed) mode, the
sum of the following two times (oscillation settling time and standby time) is required.
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