M16CSLASH29 datasheet(82/499 Pages) RENESAS

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7. Clock Generation Circuit

page 58

7.5 CPU Clock and Peripheral Function Clock

The CPU clock is used to operate the CPU and peripheral function clocks are used to operate the peripheral

functions.

7.5.1 CPU Clock

This is the operating clock for the CPU and watchdog timer.

The clock source for the CPU clock can be chosen to be the main clock, sub clock, on-chip oscillator clock

or the PLL clock.

If the main clock or on-chip oscillator clock is selected as the clock source for the CPU 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

CM0 register and bits CM17 to CM16 in CM1 register to select the divide-by-n value.

When the PLL clock is selected as the clock source for the CPU clock, the CM06 bit should be set to 0 and

bits CM17 and CM16 to 002 (undivided).

After reset, the on-chip oscillator clock divided by 16 provides the CPU clock.

Note that when entering stop mode from high or middle speed mode, on-chip oscillator mode or on-chip

oscillator low power dissipation mode, or when the CM05 bit in the CM0 register is set to 1 (main clock

turned off) in low-speed mode, the CM06 bit in the CM0 register is set to 1 (divide-by-8 mode).

7.5.2 Peripheral Function Clock(f1, f2, f8, f32, f1SIO, f2SIO, f8SIO, f32SIO, fAD, fC32, fCAN0)

These are operating clocks for the peripheral functions.

Of these, fi (i = 1, 2, 8, 32) and fiSIO are derived from the main clock, PLL clock, or on-chip oscillator clock

divided by i. The clock fi is used for Timer A, Timer B, SI/O3 and SI/O4 while fiSIO is used for UART0 to

UART2. Additionally, the f1 and f2 clocks are also used for dead time timer, Timer S, multi-master I2C bus.

The fAD clock is produced from the main clock, PLL clock or on-chip oscillator clock, and is used for the A/

D converter.

The fCAN0 clock is derived from the main clock, PLL clock or on-chip oscillator clock devided by 1 (undi-

vided), 2, 4, 8, or 16, and is used for the CAN module.

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), or when the MCU is in low power dissipation mode, the fi, fiSIO,

fAD, and fCAN0 clocks are turned off. (Note 1)

The fC32 clock is produced from the sub clock, and is used for timers A and B. This clock can only be used

when the sub clock is on.

Note 1: fCAN0 clock stops at "H" in CAN0 sleep mode.

7.5.3 ClockOutput Function

The f1, f8, f32 or fC clock can be output from the CLKOUT pin. Use the PCLK5 bit in the PCLKR register

and bits CM01 to CM00 in the CM0 register to select. Table 7.3 shows the function of the CLKOUT pin.

PCLK5

CM01

CM00

The function of the CLKOUT pin

I/O port P90

f32

Do not set

Table 7.3 The function of the CLKOUT pin

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