h8s-2158 Renesas Electronics Corporation., h8s-2158 Datasheet - Page 813

• Manufacturer Part Number: h8s-2158
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

This LSI incorporates a clock pulse generator which generates the system clock ( ), internal clock,
bus master clock, and subclock ( SUB). The clock pulse generator consists of an oscillator, duty
correction circuit, system clock select circuit, medium-speed clock divider, bus master clock select
circuit, subclock input circuit, and waveform forming circuit. Figure 26.1 shows a block diagram
of the clock pulse generator.
This LSI also incorporates a PLL (Phase Locked Loop) circuit that generates a 48-MHz clock
( 48) and a 24-MHz clock ( 24) as the USB operating clock. The 24-MHz clock can be used as
the system clock ( ) by inputting it to the duty correction circuit instead of the oscillator output to
which the EXTAL and XTAL pins are input. The PLL circuit consists of a USB external clock
input circuit, PLL input clock select circuit, division/multiplication circuit, and USB operating
clock select circuit.
USEXCL
The bus master clock is selected as either high-speed mode or medium-speed mode by software
according to the settings of the SCK2 to SCK0 bits in the standby control register. Use of the
medium-speed clock ( /2 to /32) may be limited during CPU operation and when accessing the
internal memory of the CPU. The operation speed of the DTC and RFU and the external space
access cycle are thus stabilized regardless of the setting of medium-speed mode. For details on the
standby control register, see section 27.1.1, Standby Control Register (SBYCR).
CPG0500A_000020020300
EXTAL
EXCL
XTAL
PLL circuit
USB external
input circuit
clock input
Subclock
Oscillator
circuit
Figure 26.1 Block Diagram of Clock Pulse Generator
Section 26 Clock Pulse Generator
clock select
PLL input
circuit
48
Waveform
correction
forming
circuit
circuit
Duty
USB operating
Multiplication
clock select
Division/
USB operating clock
circuit
circuit
To USB
24
48
24
count clock
WDT_1
SUB
System clock
select circuit
Rev. 3.00 Jan 25, 2006 page 761 of 872
System clock
To
Section 26 Clock Pulse Generator
pin
speed clock
Medium-
divider
To peripheral
Internal clock
modules
to /32
/2
REJ09B0286-0300
clock select
Bus master
circuit
To CPU and DTC
Bus master clock