r5f21368sdfp Renesas Electronics Corporation., r5f21368sdfp Datasheet - Page 126

• Manufacturer Part Number: r5f21368sdfp
• Description: Renesas Mcu R8c Family / R8c/3xt-a Series
• Manufacturer: Renesas Electronics Corporation.

Under development
R8C/36T-A Group
R01UH0240EJ0001 Rev.0.01
Apr 28, 2011
9.4
9.4.1
9.4.2
These clocks are supplied by the on-chip oscillators. There are high-speed and low-speed on-chip oscillators as on-
chip oscillators. The clock for the on-chip oscillator selected by FRA01 bit in the FRA0 register will be the on-chip
oscillator clock.
The clock generated by the low-speed on-chip oscillator is used as the clock source for the CPU clock,
peripheral function clock, fOCO, fLOCO, and fOCO128.
After a reset, the on-chip oscillator clock with no division generated by the low-speed oscillator will be the CPU
clock.
While bits OCD1 and OCD0 in the OCD register are 11b, when the XIN clock is stopped, the low-speed on-
chip oscillator automatically starts operating and supplies the clock.
The frequency of the on-chip oscillator clock will vary greatly depending on the supply voltage and operating
ambient temperature. Application products must be designed with sufficient margin to allow for these variations
in frequency.
The clock generated by the high-speed on-chip oscillator is used as the clock source for the CPU clock,
peripheral function clock, fOCO, fHOCO-F, fHOCO, and fOCO128.
The on-chip oscillator clock generated by the high-speed on-chip oscillator is stopped after a reset. When the
FRA00 bit in the FRA0 register is set to 1 (on-chip oscillator on), the clock starts oscillating.
To adjust the frequency of the high-speed on-chip oscillator clock to 36.864 MHz, set bits FRA25 and FRA24
in the FRA2 register to 01b. This enables the setting errors of bit rates such as 9600 bps and 38400 bps to be 0%
when the serial interface is used in UART mode.
To adjust the frequency of the high-speed on-chip oscillator clock to 32 MHz, set bits FRA25 and FRA24 to
10b.
On-Chip Oscillator Clocks
Low-Speed On-Chip Oscillator Clock
High-Speed On-Chip Oscillator Clock
Preliminary document
Specifications in this document are tentative and subject to change.
9. Clock Generation Circuit
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