Renesas R8C/11 Application Note

R8C/11, R8C/13 Group
Adjusting the Frequency of the High-speed On-chip Oscillator
Using a Commercial Frequency
1. Abstract
This application note describes a program that adjusts the oscillation frequency of the high-speed on-chip
oscillator using a commercial frequency (50/60 Hz).
2. Introduction
The explanation of this issue is applied to the following condition:
Microcomputer
RAM size, ROM size
This program can also be used when operating other microcomputers within the R8C/Tiny, provided they
have the same SFR (Special Function Registers) as the R8C/11 microcomputers. However, some functions
may have been modified.
Refer to the Hardware Manual for details. Use functions covered in this Application Note only after careful
evaluation.
3. Contents
3.1 Outline of the High-speed On-chip Oscillator
The R8C/11 group of microcomputers incorporate approximately an 8 MHz high-speed on-chip oscillator. The
operating oscillation frequency of the on-chip oscillator tends to fluctuate due to external factors such as the
operating temperature and power supply voltage. The oscillation frequency can be adjusted by setting up the
HR1 register appropriately.
The relationship between the set value of the HR1 register and the oscillation period of the high-speed
on-chip oscillator is shown below. However, because the amount of delay in each bit is not even, be sure to
change each bit to adjust. Also make sure bit 7 is set to "0".
Oscillation period of the high-speed on-chip oscillator
This application note explains how to adjust the oscillation frequency of the high-speed on-chip oscillator
using a commercial frequency (50/60 Hz).
REJ05B0471-0100Z/Rev.1.00
: R8C/11, R8C/13 Group
:1 Kbytes, 16 Kbytes
b5
=td(HRoffset)+(b6+
2
July 2004
APPLICATION NOTE
b4 b3 b2
+ + +
4 8 16
b1 b0
+ + ) × td(HR)
32 64
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