Rainbow-electronics ATmega128L Instrukcja Użytkownika Pobierz pdf (Strona 159)

159

ATmega128(L)

2467B–09/01

The following code examples show how to initialize the SPI as a master and how to per-

form a simple transmission. DDR_SPI in the examples must be replaced by the actual

data direction register controlling the SPI pins. DD_MOSI, DD_MISO and DD_SCK

must be replaced by the actual data direction bits for these pins. E.g. if MOSI is placed

on pin PB5, replace DD_MOSI with DDB5 and DDR_SPI with DDRB.

Note: 1. The example code assumes that the part specific header file is 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

C Code 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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