Rainbow-electronics ATmega8515L Manual do Utilizador descarregar pdf (Página 129)

129

ATmega8515(L)

2512A–AVR–04/02

SPI Status Register – SPSR

• Bit 7 – SPIF: SPI Interrupt Flag

When a serial transfer iscomplete, the SPIF flag isset. An interruptis generated ifSPIE

in SPCRisset and global interrupts are enabled. If SS

is an input and isdriven low

when the SPI is in Master mode, thiswill also set the SPIF flag. SPIF isclearedbyhard-

ware when executing the corresponding interrupt handling vector.Alternatively, the

SPIF bit isclearedbyfirst reading the SPIStatus RegisterwithSPIF set, then accessing

the SPIData Register(SPDR).

• Bit 6 – WCOL: Write COLlision Flag

The WCOL bit isset if the SPIData Register(SPDR) iswritten during a data transfer.

The WCOL bit (and the SPIF bit) are clearedbyfirst reading the SPIStatus Register

withWCOLset, and then accessing the SPIData Register.

• Bit 5..1 – Res: Reserved Bits

These bits are reservedbits in the ATmega8515 andwill always read aszero.

• Bit 0 – SPI2X: Double SPI Speed Bit

When thisbit iswritten logic one the SPIspeed(SCKFrequency) will be doubledwhen

the SPI is in Master mode (see Table58).This means that the minimum SCK periodwill

betwo CPUclock periods. When the SPI isconfigured asSlave, the SPI is only guaran-

teed to work at f

osc

/4 orlower.

The SPI interfaceonthe ATmega8515 is alsousedforprogram memory andEEPROM

downloading or uploading. See page 189forSerial Programming and verification.

SPI Data Register – SPDR

The SPIData Register is a read/write register usedfordata transferbetween the Regis-

terFileand the SPIShift Register. Writing to the register initiatesdata transmission.

Reading the registercauses the Shift Register Receive buffer to be read.

Bit 76543 210

SPIFWCOL–––––SPI2X SPSR

Read/WriteRRRRRRRR/W

Initial Value00000000

Bit 76543 210

MSB LSB SPDR

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value XXXXXXXXUndefined

1 2 ... 124 125 126 127 128 129 130 131 132 133 134 ... 222 223

Sem comentários

Rainbow-electronics ATmega8515L Manual do Utilizador Página 129