Renesas rl78 User Manual
RL78/G1A
CHAPTER 5 CLOCK GENERATOR
R01UH0305EJ0200 Rev.2.00
156
Jul 04, 2013
5.3.8 High-speed on-chip oscillator frequency select register (HOCODIV)
The frequency of the high-speed on-chip oscillator which is set by an option byte (000C2H) can be changed by using
high-speed on-chip oscillator frequency select register (HOCODIV). However, the selectable frequency depends on the
FRQSEL3 bit of the option byte (000C2H).
The HOCODIV register can be set by an 8-bit memory manipulation instruction.
Reset signal generation clears this register to the value set by FRQSEL2 to FRQSEL0 of the option byte (000C2H).
Figure 5-9. Format of High-speed On-chip Oscillator Frequency Select Register (HOCODIV)
Address: F00A8H After reset: the value set by FRQSEL2 to FRQSEL0 of the option byte (000C2H) R/W
Symbol
7 6 5 4 3 2 1 0
HOCODIV
0 0 0 0 0
HOCODIV2 HOCODIV1
HOCODIV0
High-Speed On-Chip Oscillator Clock Frequency
HOCODIV2 HOCODIV1 HOCODIV0
FRQSEL3 Bit is 0
FRQSEL3 Bit of is 1
0
0
0
24 MHz
32 MHz
0
0
1
12 MHz
16 MHz
0
1
0
6 MHz
8 MHz
0
1
1
3 MHz
4 MHz
1
0
0
Setting prohibited
2 MHz
1
0
1
Setting prohibited
1 MHz
Other than aboves
Setting prohibited
Cautions 1. When changing the frequency by using the HOCODIV register, specify a
frequency in the voltage range corresponding to the flash operating mode
specified in the option byte (000C2H).
Option Byte (000C2H)
Value
CMODE1 CMODE0
Flash Operation Mode
Operating
Frequency Range
Operating Voltage
Range
0
0
LV (low-voltage main) mode
1 to 4 MHz
1.6 to 3.6 V
1
0
LS (low-speed main) mode
1 to 8 MHz
1.8 to 3.6 V
1 to 16 MHz
2.4 to 3.6 V
1
1
HS (high-speed main) mode
1 to 32 MHz
2.7 to 3.6 V
2. Change the HOCODIV register value while the high-speed on-chip oscillator clock
(f
IH
) is selected as the CPU/peripheral hardware clock (f
CLK
).
3. After the frequency is changed using the HOCODIV register, the new frequency is
applied after the period below has elapsed.
- Operation for up to three clocks at the pre-change frequency
- CPU/peripheral hardware clock wait at the post-change frequency for up to three
clocks
<R>
<R>