Cpu Clock And Peripheral Function Clock; Cpu Clock; Peripheral Function Clock (F1, F2, F8, F32, Fad, F1Sio, F8Sio, F32Sio, Fring, Fring128); Fring And Fring128 - Renesas M16C FAMILY Hardware Manual

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

6.3 CPU Clock and Peripheral Function Clock

There are two type clocks: CPU clock to operate the CPU and peripheral function clock to operate the
peripheral functions. Also refer to "Figure 6.1 Clock Generating Circuit".

6.3.1 CPU Clock

This is an operating clock for the CPU and watchdog timer.
The clock source for the CPU clock can be chosen to be the main clock or ring oscillator clock.
The selected clock source can be divided by 1 (undivided), 2, 4, 8 or 16 to produce the CPU clock. Use
the CM06 bit in the CM0 register and the CM17 to CM16 bits in the CM1 register to select the divide-
by-n value.
After reset, the ring oscillator clock divided by 8 provides the CPU clock. When the clock source for the
CPU clock is switched over, set the CM06 bit to "1" (divide-by-8 mode) before changing the OCD2 bit.
Note that when entering stop mode from high or middle speed mode, the CM06 bit is set to "1" (divide-
by-8 mode).
6.3.2 Peripheral Function Clock (f
These are operating clocks for the peripheral functions.
Of these, fi (i=1, 2, 8, 32) is derived from the main clock or ring oscillator clock by dividing them by i.
The clock fi is used for timers X, Y, Z and C.
The clock fj
SIO
The clock fj
SIO
The f clock is produced from the main clock or the ring oscillator clock and is used for the A-D
AD
converter.
When the WAIT instruction is executed after setting the CM02 bit in the CM0 register to "1" (peripheral
function clock turned off during wait mode), the clocks fi, fj
6.3.3 f and f
RING
These are operating clocks for the peripheral functions.
The f runs at the same frequency as the ring oscillator, and can be used as the souce for the timer
RING
Y. The f
RING128
capture function.
When the WAIT instruction is executed, the clocks f
6.3.4 f -fast
RING
This is used as the count source for the timer C. The f
oscillator and provided by setting the HR00 bit to "1" (high-speed ring oscillator on).
When the WAIT instruction is executed, the clock f
Rev.0.91 2003 Sep 08
, f
1 2
(j=1, 8, 32) is derived from the main clock or ring oscillator clock by dividing them by j.
is used for serial I/O.
RING128
is derived from the f
RING
page 35 of 184
6.3 CPU Clock and Peripheral Function Clock
, f , f , f , f , f
8 32 AD 1SIO 8SIO
, and f
SIO
by dividing it by 128, and can be used for the timer C input
and f
RING RING128
-fast is derived from the high-speed ring
RING
-fast is not turned off.
RING
, f , f , f )
32SIO RING RING128
are turned off.
AD
are not turned off.