On-Chip Oscillator Clock - Renesas M16C Series Hardware Manual

R8C/11 Group

6.2 On-chip Oscillator Clock

This clock is supplied by an 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, f
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 "11
tion stop detection function enabled), the low-speed on-chip oscillator automatically starts operating,
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, f
After reset, the on-chip oscillator clock derived from high-speed on-chip oscillator is halted. The oscil-
lation 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 5 b6 + 32 5 b5 + 16 5 b4 + 8 5 b3 + 4
b2 + 2
b0 to b6 : Bits in HR1 register
Rev.1.20 Jan 27, 2006
REJ09B0062-0120
, f
RING RING128
, f
RING RING128
b1 + b0)
page 35 of 204
and f .
RING-S
, and f .
RING1-fast
6.2 On-chip Oscillator Clock
" (oscilla-
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