Rainbow-electronics ATmega8515L Manual de usuario descargar pdf (Pagina 35)

ATmega8515(L)

2512A–AVR–04/02

External RC Oscillator For timing insensitive applications, theexternal RCconfiguration showninFigure19

can beused.The frequency isroughly estimatedbytheequation f=1/(3RC). Cshould

beatleast22pF. By programming the CKOPT Fuse, theusercan enableaninternal

36 pF capacitorbetween XTAL1and GND, thereby removing the needfor an external

capacitor.

Figure 19. External RCConfiguration

The Oscillatorcan operate in fourdifferent modes, each optimizedfor a specificfre-

quency range. Theoperating modeisselectedbythe fuses CKSEL3..0 asshownin

Table 10.

When thisOscillator isselected, start-up times are determinedbythe SUT Fuses as

showninTable 11.

Note: 1. This option should not beusedwhen operating closetothemaximum frequency of

the device.

Table 10. External RCOscillatorOperating Modes

CKSEL3..0 Frequency Range (MHz)

0101 - 0.9

0110 0.9-3.0

0111 3.0 - 8.0

1000 8.0 - 12.0

Table 11. Start-up Timesfor the External RCOscillatorClock Selection

SUT1..0

Start-up Time

from Power-down

Additional Delay from

Reset (V

= 5.0V) Recommended Usage

00 18 CK – BOD enabled

01 18 CK 4.1 msFast rising power

10 18 CK 65msSlowly rising power

11 6CK

(1)

4.1 msFast rising power orBOD

enabled

XTAL2

XTAL1

GND

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 222 223

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Rainbow-electronics ATmega8515L Manual de usuario Pagina 35