Cpu Clock And Peripheral Function Clock - Renesas M16C Series Hardware Manual

R8C/11 Group

6.3 CPU Clock and Peripheral Function Clock

There are two types of clocks: CPU clock to operate the CPU and peripheral function clock to operate the
peripheral functions. Also refer to "Figure 6.1 Clock Generation 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 on-chip 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 low-speed on-chip oscillator clock divided by 8 provides the CPU clock.
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 on-chip oscillator clock by dividing them by
i. The clock fi is used for timers X, Y, Z and C.
The clock fj
SIO
j. The clock fj
SIO
The f clock is produced from the main clock or the on-chip 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 on-chip oscillator, and can be used as the souce for the
RING
timer Y. The f
RING128
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 on-chip oscillator on).
When the WAIT instruction is executed, the clock f
Rev.1.20 Jan 27, 2006
REJ09B0062-0120
, f
1 2
(j=1, 8, 32) is derived from the main clock or on-chip oscillator clock by dividing them by
is used for serial interface.
RING128
is derived from the f
page 36 of 204
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 Timer C.
RING
and f
RING RING128
-fast is derived from the high-speed on-chip
RING
-fast is not turned off.
RING
, f , f , f )
32SIO RING RING128
are turned off.
AD
are not turned off.