Ring Oscillator Clock; Low-Speed Ring Oscillator; High-Speed Ring Oscillator - Renesas M16C FAMILY Hardware Manual

Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
R8C/11 Group

6.2 Ring Oscillator Clock

This clock is supplied by a ring oscillator. There are two kinds of ring oscillator: high-speed ring oscil-
lator and low-speed ring oscillator. These oscillators are selected by the bit HR01 bit in the HR0
register.

6.2.1 Low-speed Ring Oscillator

The clock derived from the low-speed ring oscillator is used as the clock source for the CPU clock,
peripheral function clock, f
After reset, the ring oscillator clock derived from low-speed ring 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 "11
lation stop detection function enabled), the low-speed ring oscillator automatically starts operating,
supplying the necessary clock for the microcomputer.
The frequency of the low-speed ring oscillator varies depending on the supply voltage and the opera-
tion ambient temperature. The application products must be designed with sufficient margin to ac-
commodate the frequency range.

6.2.2 High-speed Ring Oscillator

The clock derived from high-speed ring oscillator is used as the clock source for the CPU clock,
peripheral function clock, f
After reset, the ring oscillator clock derived from high-speed ring oscillator is halted. The oscillation is
started by setting the HR00 bit in the HR0 register to "1" (high-speed ring oscillator on). The fre-
quency can be adjusted by the HR1 register.
The relationship between the value of HR1 register and the period of high-speed ring 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 ring oscillator = td(HR offset) + (b6 + b5/2 + b4/4 + b3/8 + b2/16 + b1/32 + b0/64)
b0 to b6 : Bits in HR1 register
Rev.0.91 2003 Sep 08
, f
RING RING128
, f
RING RING128
page 34 of 184
and f .
RING-S
, and f .
RING1-fast
6.2 Ring Oscillator Clock
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