Rainbow-electronics ATmega8515L Manual de usuario descargar pdf (Pagina 37)

ATmega8515(L)

2512A–AVR–04/02

External Clock To drive the device from an externalclock source,XTAL1 should be driven asshownin

Figure20.Torun the deviceonanexternalclock, the CKSEL Fuses must be pro-

grammed to “0000”. By programming the CKOPT Fuse, theusercan enableaninternal

36 pF capacitorbetween XTAL1andGND.

Figure 20. ExternalClock Drive Configuration

When thisclock sourceisselected, start-up times are determinedbythe SUT Fuses as

showninTable 15.

Table 14. Internal RCOscillatorFrequency Range.

OSCCAL Value

Min Frequency in Percentage of

Nominal Frequency

Max Frequency in Percentage of

Nominal Frequency

$00 50% 100%

$7F 75% 150%

$FF 100% 200%

Table 15. Start-up Timesfor the ExternalClock Selection

SUT1..0

Start-up Time from

Power-down

Additional Delay from

Reset (V

= 5.0V) Recommended Usage

00 6CK – BOD enabled

01 6CK 4.1 msFast rising power

10 6CK 65msSlowly rising power

11 Reserved

EXTERNAL

CLOCK

SIGNAL

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 222 223

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Rainbow-electronics ATmega8515L Manual de usuario Pagina 37