R8C/1A Group, R8C/1B Group
10. Clock Generation Circuit
Rev.1.30
Dec 08, 2006
Page 64 of 315
REJ09B0252-0130
Figure 10.6
Registers HRA1 and HRA2
High-Speed On-Chip Oscillator Control Register 1
(1)
Symbol
Address
After Reset
HRA1
0021h
When Shipping
RW
NOTE :
1.
2. Adjust the HRA1 register so that the frequency of the high-speed on-chip oscillator w ill be the maximum value or
less of the system clock.
b7 b6 b5 b4 b3 b2 b1 b0
Set the PRC0 bit in the PRCR register to 1 (w rite enable) before rew riting the HRA1 register.
RW
Function
The frequency of the high-speed on-chip oscillator is adjusted w ith bits 0 to 7.
(2)
High-speed on-chip oscillator frequency = 8 MHz
(HRA1 register = value w hen shipping ; fRING-fast mode 0)
Setting the HRA1 register to a low er value (minimum value: 00h), results in a higher
frequency.
Setting the HRA1 register to a higher value (maximum value: FFh), results in a low er
frequency.
High-Speed On-Chip Oscillator Control Register 2
(1)
Symbol
A ddress
A f ter Reset
HRA 2
0022h
00h
Bit Symbol
Bit Name
Function
RW
NOTES :
1. Set the PRC0 bit in the PRCR register to 1 (w rite enable) bef ore rew riting the HRA 2 register.
2.
3.
4.
5. Set the HRA 20 and HRA 21 bits so that the f requency of the high-speed on-chip oscillator w ill be the maximum value
or less of the system clock.
b7 b6 b5 b4 b3 b2 b1 b0
0 0 0
HRA 20
RW
HRA 21
RW
High-speed on-chip oscillator mode
select bits
(5)
b1 b0
0 0 : f RING-f ast mode 0
(2)
0 1 : f RING-f ast mode 1
(3)
1 0 : f RING-f ast mode 2
(4)
1 1 : Do not set.
High-speed on-chip oscillator f requency = 8 MHz (HRA 1 register = value w hen shipping)
If f RING-f ast mode 0 is sw itched to f RING-f ast mode 1, the f requency is multiplied by 1.5.
If f RING-f ast mode 0 is sw itched to f RING-f ast mode 2, the f requency is multiplied by 0.5.
—
(b4-b2)
Reserved bits
Set to 0.
RW
—
(b7-b5)
—
Nothing is assigned. If necessary, set to 0.
When read, the content is 0.
