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Adjusting the Frequency of the High-speed On-chip Oscillator Using a Commercial Frequency
Adjust the high-speed on-chip oscillator during initial operating time and save the set value in the flash ROM.
Make sure the address to which it is saved does not match that of a block where the program is located. A
sample program memory map is shown in Figure 2.
From the next time on (after the HR1 adjustment value is saved), read the initial value of the HR1 register
from the data flash and set it in the HR1 register. Thereafter, fine-adjust the oscillation frequency each time a
rising edge of the commercial frequency is detected.
Note 1: In this application note, the HR1 adjustment value is written using EW1 mode. For this reason,
consideration is taken to ensure that the block where the rewrite program is located and the block into
which the HR1 adjustment value is written will not match.
Figure 2. Sample Program Memory Map
3.3 Pins Used
Table 2. List of Pins Used and Their Functions
Pin name
I/O
______
P3
/INT
3/TC
Input
3
IN
R8C/11
______
P3
/INT
3
Figure 3. Commercial Frequency Input
REJ05B0471-0100Z/Rev.1.00
0000h
0400h
041Fh
0420h
0620h
C000h
D000h
Program area (Note 1)
D7DBh
E000h
FEDBh
HR1 adjustment value (Note 1)
FEDCh
FFDCh
FFFFh
Fuction
Commercial frequency (square wave) input
Commercial frequency converter circuit
(sine wave -> square wave)
3/TC
IN
Note: Power supply voltage is Vcc.
Data area
Stack Area
Relocatable vector
Fixed vector
July 2004
R8C/11, R8C/13 Group
Block 1
Block 0
Commercial power
supply
Page 3 of 21
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