Section 20 Clock Pulse Generator; Overview - Renesas F-ZTAT H8 Series Hardware Manual

Section 20 Clock Pulse Generator

20.1

Overview

The H8/3048 Group has a built-in clock pulse generator (CPG) that generates the system clock (φ)
and other internal clock signals (φ/2 to φ/4096). After duty adjustment, a frequency divider divides
the clock frequency to generate the system clock (φ). The system clock is output at the φ pin *
furnished as a master clock to prescalers that supply clock signals to the on-chip supporting
modules. Frequency division ratios of 1/1, 1/2, 1/4, and 1/8 can be selected for the frequency
divider by settings in a division control register (DIVCR). Power consumption in the chip is
reduced in almost direct proportion to the frequency division ratio *
Notes: 1. Usage of the φ pin differs depending on the chip operating mode and the PSTOP bit
setting in the module standby control register (MSTCR). For details, see section 21.7,
System Clock Output Disabling Function.
2. The division ratio of the frequency divider can be changed dynamically during
operation. The clock output at the φ pin also changes when the division ratio is
changed. The frequency output at the φ pin is shown below.
φ = EXTAL × n
where, EXTAL: Frequency of crystal resonator or external clock signal
n: Frequency division ratio (n = 1/1, 1/2, 1/4, or 1/8)
Section 20 Clock Pulse Generator
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Rev. 7.00 Sep 21, 2005 page 653 of 878
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