r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 1192

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 24 Clock Pulse Generator
24.4
The PLL circuit for the USB module takes 8, 12, and 16 MHz clock signals from an oscillator and
generates the 48-MHz clock for the USB module through frequency-multiplication by 3,4, or 6.
The frequency-multiplication factor is set by bits USSTC1 and USSTC0 in the USPLLCR. For
details on the USPLLCR, see section 24.1.3, USB PLL Control Register (USPLLCR).
When the USB is in use, make settings so that the system clock runs at or above 14 MHz. The
settings listed below (table 23.4) produce a USB dedicated clock at 48 MHz. Operation at other
frequencies cannot be guaranteed.
Table 24.4 Clock Selection when the USB is to be used
Rev. 1.00 Sep. 19, 2008 Page 1162 of 1342
REJ09B0467-0100
Input clock frequency from the
oscillator (MHz)
8 MHz
12 MHz
16 MHz
PLL Circuit for the USB Module
USB dedicated clock
(cku: 48 MHz)
EXTALx6
EXTALx4
EXTALx3
System clock (φ)
EXTALx2 (16MHz)
EXTALx2 (24MHz)
EXTALx2 (32MHz)
EXTALx1 (16MHz)