h8s-2649 Renesas Electronics Corporation., h8s-2649 Datasheet - Page 597

• Manufacturer Part Number: h8s-2649
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

This LSI has an on-chip clock pulse generator that generates the system clock (φ), the bus master
clock, and internal clocks. The clock pulse generator consists of an oscillator, PLL circuit, clock
selection circuit, medium-speed clock divider, and bus master clock selection circuit. A block
diagram of the clock pulse generator is shown in figure 20.1.
The frequency can be changed by means of the PLL circuit. Frequency changes are performed by
software by settings in the low-power control register (LPWRCR) and system clock control
register (SCKCR).
EXTAL
XTAL
OSC1
OSC2
[Legend]
LPWRCR:
SCKCR:
Low-power control register
System clock control register
oscillator
Subclock
oscillator
System
clock
Figure 20.1 Block Diagram of Clock Pulse Generator
Section 20 Clock Pulse Generator
(x1, x2, x4)
PLL circuit
generation
Waveform
LPWRCR
circuit
WDT_1 count clock
STC0, STC1
φ
SUB
selection
circuit
Clock
System
clock to
φ pin
clock divider
Rev. 2.00 Dec. 05, 2005 Page 559 of 724
Medium-
speed
peripheral modules
Internal clock to
Section 20 Clock Pulse Generator
φ/2 to
φ/32
φ
selection
SCKCR
master
circuit
clock
Bus
REJ09B0200-0200
Bus master clock
to CPU and DTC
SCK2 to SCK0