M16CSLASH1N datasheet(41/238 Pages) RENESAS

41 / 238 page

Rev.1.00

Oct 20, 2004

page 29 of 222

M16C/1N Group

6. Clock Generation Circuit

REJ09B0007-0100Z

Microcomputer

(Built-in feedback resistor)

XCIN

XCOUT

Externally derived clock

Open

Vcc

Vss

Microcomputer

(Built-in feedback resistor)

XCIN

XCOUT

(Note 1)

CCIN

CCOUT

RCd

Note 1: Insert a damping resistor if required. The resistance will vary depending on the oscillator and the oscillation

drive capacity setting. Use the value recommended by the maker of the oscillator.

When the oscillation drive capacity is set to low, check that oscillation is stable.

6.2 Sub-clock

The sub-clock is generated by the sub-clock oscillation circuit. No sub-clock is generated after a reset.

After oscillation is started using the port Xc select bit (bit 4 at address 000616), the sub-clock can be

selected as BCLK by using the system clock select bit (bit 7 at address 000616). However, be sure that

the sub-clock oscillation has fully stabilized before switching.

After the oscillation of the sub-clock oscillation circuit has stabilized, the drive capacity of the XCOUT pin

can be reduced using the XCIN-XCOUT drive capacity select bit (bit 3 at address 000616). Reducing the

drive capacity of the XCOUT pin reduces the power dissipation. This bit changes to "1" when shifting to

stop mode and at a reset.

Figure 6.7 shows the examples of sub-clock connection circuit.

Figure 6.7 Examples of sub-clock connection circuit

6.3 On-chip Oscillator Clock

This clock by supplied by a on-chip oscillator. The oscillation of the on-ship oscillator can be used as

BCLK by setting the main clock selected bit (bit 2 at address 000C16. Lower power consumption can be

realized because the oscillating frequency of the on-chip oscillator is much lower compared to that of XIN.

The frequency of the on-chip oscillator depends on the supply voltage and the operation temperature

range. The application products must be designed with sufficient margin to accommodate the frequency

range.

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