R8C/13 Group
6.2 On-chip Oscillator Clock
6.2 On-Chip Oscillator Clock
This clock is supplied by a on-chip oscillator. There are two kinds of on-chip oscillator: high-speed on-
chip oscillator and low-speed on-chip oscillator. These oscillators are selected by the bit HR01 bit in
the HR0 register.
6.2.1 Low-Speed On-Chip Oscillator Clock
The clock derived from the low-speed on-chip oscillator is used as the clock source for the CPU
clock, peripheral function clock, fRING, fRING128 and fRING-S.
After reset, the on-chip oscillator clock derived from low-speed on-chip oscillator by divided by 8 is
selected for the CPU clock.
If the main clock stops oscillating when the OCD1 to OCD0 bits in the OCD register are “112” (oscil-
lation stop detection function enabled), the low-speed on-chip oscillator automatically starts operat-
ing, supplying the necessary clock for the microcomputer.
The frequency of the low-speed on-chip oscillator varies depending on the supply voltage and the
operation ambient temperature. The application products must be designed with sufficient margin for
the frequency change.
6.2.2 High-Speed On-Chip Oscillator Clock
The clock derived from high-speed on-chip oscillator is used as the clock source for the CPU clock,
peripheral function clock, fRING, fRING128, and fRING1-fast.
After reset, the on-chip oscillator clock derived from high-speed on-chip oscillator is halted. The
oscillation is started by setting the HR00 bit in the HR0 register to “1” (high-speed on-chip oscillator
on). The frequency can be adjusted by the HR1 register.
The relationship between the value of HR1 register and the period of high-speed on-chip oscillator is
shown below. It is noted that the difference in delay between the bits should be adjusted by changing
each bit. Bit 7 should be set be “0”.
Period of high-speed on-chip oscillator = td(HR offset) + (64 ✕✕b6 + 32 ✕✕✕b5 + 16 ✕✕b4 + 8 ✕✕b3 + 4
✕✕✕✕✕b2 + 2 ✕✕b1 + b0) ✕✕td(HR)
b0 to b6 : Bits in HR1 register
Rev.1.20 Jan 27, 2006 page 35 of 205
REJ09B0111-0120
RENESAS [ RENESAS TECHNOLOGY CORP ]
