Renesas RL78 Series

RL78/F13, F14 CHAPTER 10 CLOCK OUTPUT/BUZZER OUTPUT CONTROLLER
R01UH0368EJ0210 Rev.2.10 690
Dec 10, 2015
4. The high-speed on-chip oscillator clock (fIH) and the high-speed system clock (fMX) can be selected
as the main system clock (fMAIN) by the setting of the MCM0 bit (bit 4 of the system clock control
register (CKC)). For details, refer to CHAPTER 5 CLOCK GENERATOR.
5. The subsystem clock (f
SUB) and the low-speed on-chip oscillator clock (fIL) can be selected as the
sub/low-speed on-chip oscillator select clock by the setting of the SELLOSC bit (bit 0 of the clock
select register (CKSEL)). For details, refer to CHAPTER 5 CLOCK GENERATOR.
10.3.2 Clock Select Register (CKSEL)
This register is used to select the CPU clock (fSUB/fIL) the clocks for the timer RJ, timer RD, and clock output/buzzer
output. Together with the CMC register, the SELLOSC bit is used to set the operation mode of the subsystem clock.
For details, see Figure 5-3 Format of Clock Operation Mode Control Register (CMC).
Set the CKSEL register by a 1-bit or 8-bit memory manipulation instruction.
Writing to the CKSEL register is disabled when the GCSC bit of the IAWCTL register is set to 1.
Figure 10-3. Format of Clock Select Register (CKSEL)
Address: F02C4H After reset: 00H R/W
Symbol 7 6 5 4 3 <2> 1 <0>
CKSEL 0 0
0 0
0
TRD_CKS
EL
0
SELLOSC
Notes 3, 4
SELLOSC
Notes 3, 4
Control of sub/low-speed on-chip oscillator selection clock (f
SL) selection
0 Selects fSUB
Note 1
1 Selects fIL
Note 2
Notes 1. When setting f
SUB as the CPU/peripheral hardware clock, first set the SELLOSC bit to 0 and then set the CSS
bit in the CKC register to 1.
2. When setting f
IL as the CPU/peripheral hardware clock, first set the SELLOSC bit to 1 and then set the CSS
bit in the CKC register to 1.
3. When the SELLOSC bit is set to 1, the low-speed on-chip oscillator operates.
4. When setting the CKSEL register in the 20-, 30-, or 32-pin products, set the SELLOSC bit to 1.