R01UH0823EJ0100 Rev.1.00 Page 190 of 1823
Jul 31, 2019
RX23W Group 9. Clock Generation Circuit
9.2.17 CLKOUT Output Control Register (CKOCR)
Note: Set the PRCR.PRC0 bit to 1 (write enabled) before rewriting this register.
Note 1. It is also necessary to set the pin function control register and port mode register for the corresponding pin.
CKOSEL[3:0] Bits (CLKOUT Output Source Select)
Set these bits to select the LOCO clock, HOCO clock, main clock, sub-clock, or PLL as the source of the clock to be
output from the CLKOUT pin.
CKODIV[2:0] Bits (CLKOUT Output Division Ratio Select)
Set these bits to select the division ratio of the clock selected by the CKOSEL[3:0] bits.
Set the CKOSTP bit to 1 when changing the division ratio.
The division ratio of the output clock frequency should be set to no higher than 8 MHz when VCC is 2.7 V or above, and
no higher than 4 MHz when VCC is below 2.7 V.
For details on the characteristics of the clock output from the CLKOUT pin, see
Table 51.32, Timing of On-Chip
Peripheral Modules (1)
.
CKOSTP Bit (CLKOUT Output Stop Control)
Set this bit to enable or disable output from the CLKOUT pin.
When this bit is set to 1, the selected clock is output. When this bit is set to 1, a low level is output.
If the CKOSTP bit is rewritten while the clock is still oscillating, a glitch may be generated in the output.
Address(es): 0008 003Eh
b15 b14 b13 b12 b11 b10 b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
CKOST
P
CKODIV[2:0] CKOSEL[3:0] ————————
Value after reset:
1000000000000000
Bit Symbol Bit Name Description R/W
b7 to b0 — Reserved These bits are read as 0. The write value should be 0. R/W
b11 to b8 CKOSEL[3:0] CLKOUT Output Source Select
b11 b8
0 0 0 0: LOCO clock
0 0 0 1: HOCO clock
0 0 1 0: Main clock oscillator
0 0 1 1: Sub-clock oscillator
0 1 0 0: PLL
Settings other than above are prohibited.
R/W
b14 to b12 CKODIV[2:0] CLKOUT Output Division Ratio
Select
b14 b2
0 0 0: No division
0 0 1: ×1/2
0 1 0: ×1/4
0 1 1: ×1/8
1 0 0: ×1/16
Settings other than above are prohibited.
R/W
b15 CKOSTP CLKOUT Output Stop Control 0: CLKOUT pin output enabled*
1
1: CLKOUT pin output disabled (always output the low
level)
R/W
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