Renesas RA Series Quick Design Guide

Renesas RA Family RA4 Quick Design Guide
R01AN5988EU0100 Rev.1.00 Page 19 of 51
Jul.21.21
Figure 12. Clock Settings Using Renesas FSP Configurator
5.6 HOCO Accuracy
The internal high-speed on-chip oscillator (HOCO) runs at 16 MHz, 18 MHz, or 20 MHz for Arm Cortex-M33
core devices, and 24 MHz, 32 MHz, 48 MHz, or 64 MHz for Arm Cortex-M4 devices, with a typical accuracy
of +/-2% or better. HOCO accuracy specifications are characterized for various ambient operating
temperature (Ta) ranges.
For Arm Cortex-M33 devices, the accuracy of the HOCO may be improved by enabling the Frequency
Locked Loop (FLL) function, which results in a clock accuracy of +/-0.25% or better. Refer to the Electrical
Specifications in the hardware manual for details.
The HOCO may be used as an input to the PLL circuit. When the HOCO is used this way, no external
oscillator is required. This may be an advantage when space constraints, cost, or other limitations require a
reduced component count in a PCB design. However, there are performance tradeoffs and limitations due to
the clock accuracy which should be evaluated for your application.
5.7 Flash Interface Clock
The Flash interface Clock (FCLK) is used as the operating clock when programming and erasing internal
flash (ROM and DF) and for reading from the data flash. Therefore, the frequency setting of the FCLK will
have a direct impact on the amount of time it takes to read from the data flash. If the user’s program is
reading from the data flash, or performing programming or erasures on internal flash, then using the
maximum FCLK frequency is recommended.
The FCLK must run at a frequency of at least 4 MHz when writing or erasing code flash (ROM) or data flash.
Please note that the FCLK frequency does not have any impact upon reading from ROM or reading and
writing to RAM.
5.8 Board Design
Refer to the “Usage Notes” section of the Clock Generation Circuit (CGC) chapter in the Hardware User’s
Manual for more information on using the CGC and for board design recommendations.

Renesas RA Series Specifications

General

Brand	Renesas
Model	RA Series
Category	Microcontrollers
Language	English