Frequency Divider; Usage Notes; Notes On Clock Pulse Generator; Notes On Oscillator - Hitachi H8S/2378, H8S/2378R Series Hardware Manual

3. The target value is set in bits STC1 and STC0, and a transition is made to software standby
mode.
4. The clock pulse generator stops and the value set in STC1 and STC0 becomes valid.
5. Software standby mode is cleared, and a transition time is secured in accordance with the
setting in STS3 to STS0.
6. After the set transition time has elapsed, this LSI resumes operation using the target
multiplication factor.
When STCS = 1, this LSI operates using the new multiplication factor immediately after bits
STC1 and STC0 are rewritten.
21.4

Frequency Divider

The frequency divider divides the PLL output clock to generate a 1/2, 1/4, 1/8, 1/16, or 1/32 clock.
21.5

Usage Notes

21.5.1

Notes on Clock Pulse Generator

1. The following points should be noted since the frequency of ∅ changes according to the
setting of SCKCR and PLLCR.
Select the clock division ratio that is within the operation guaranteed range of clock cycle time
tcyc shown in the AC timing of Electrical Characteristics. In other words, the range of ∅ must
be specified from 8 MHz (min) to 33 MHz (max); outside of this range must be prevented.
2. All the on-chip peripheral modules operate on the ∅. Therefore, note that the time processing
of modules such as a timer and SCI differ before and after changing the clock division ratio. In
addition, wait time for clearing software standby mode differs by changing the clock division
ratio. See the description, Setting Oscillation Stabilization Time after Clearing Software
Standby Mode in section 22.2.3, Software Standby Mode, for details.
3. Note that the frequency of ∅ will be changed when setting SCKCR or PLLCR while executing
the external bus cycle with the write-data-buffer function or the EXDMAC.
21.5.2

Notes on Oscillator

Since various characteristics related to the oscillator are closely linked to the user's board design,
thorough evaluation is necessary on the user's part, using the oscillator connection examples
shown in this section as a guide. As the oscillator circuit ratings will depend on the floating
capacitance of the oscillator and the mounting circuit, the ratings should be determined in
consultation with the oscillator manufacturer. The design must ensure that a voltage exceeding the
maximum rating is not applied to the oscillator pin.
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