Rainbow-electronics ATmega8515L Instrukcja Użytkownika Pobierz pdf (Strona 125)

125

ATmega8515(L)

2512A–AVR–04/02

The following codeexamplesshowhow to initializethe SPI as a Master andhow to per-

formasimpletransmission. DDR_SPI in theexamples must be replacedbytheactual

Data Direction Registercontrolling the SPIpins. DD_MOSI, DD_MISO andDD_SCK

must be replacedbytheactualdata direction bitsfor these pins. For example, ifMOSIis

placed on pin PB5,replace DD_MOSI with DDB5andDDR_SPIwithDDRB.

Note: 1. Theexample codeassumes that the part specificheaderfileis included.

Assembly Code Example

(1)

SPI_MasterInit:

; Set MOSI and SCK output, all others input

ldi r17,(1<<DD_MOSI)|(1<<DD_SCK)

out DDR_SPI,r17

; Enable SPI, Master, set clock rate fck/16

ldi r17,(1<<SPE)|(1<<MSTR)|(1<<SPR0)

out SPCR,r17

ret

SPI_MasterTransmit:

; Start transmission of data (r16)

out SPDR,r16

Wait_Transmit:

; Wait for transmission complete

sbis SPSR,SPIF

rjmp Wait_Transmit

ret

CCode Example

(1)

void SPI_MasterInit(void)

{

/* Set MOSI and SCK output, all others input */

DDR_SPI = (1<<DD_MOSI)|(1<<DD_SCK);

/* Enable SPI, Master, set clock rate fck/16 */

SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);

}

void SPI_MasterTransmit(char cData)

{

/* Start transmission */

SPDR = cData;

/* Wait for transmission complete */

while(!(SPSR & (1<<SPIF)))

;

}

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