www.elektronik.si

[trot]

Zanima me, ali je potrebno za vsak ukaz, ki ga pošljem sd kartici, postavit CS (chip select) najprej na 1 in po tem na 0 (in ti ponavkljam za vsak ukaz), ali lahko CS najprej postavim na 1, pošljem več ukazov, in potem dam CD na 0?

Je ta postopek standarden, ali se lahko razlikuje za različne čipe?

[MarkoM]

Ja, preberi v datasheetu. Je lahko čisto odvisno od čipa do čipa s SPI vmesnikom. Nedolgo nazaj sem se igral z SPI-CAN modulom in je imel rešeno tako: CS nato podatek ali bom pisal ali bral, potem naslov, potem podatek in na koncu C\S\.
Večinoma imajo tako rešeno...

[trot]

Sem gledal datasheet od ScanDisk (poglavje 3.3), pa nisem našel tega podatka...zato tudi sprašujem. Sem gledal philipsov AN10406, pa je enkrat CS uporabljen, drugič pa ne:

int mmc_init()
{
DWORD i;
/* Generate a data pattern for write block */
for(i=0;i<MMC_DATA_SIZE;i++)
{
MMCWRData[i] = i;
}
MMCStatus = 0;
IOSET0 = SPI_SEL; /* set SPI SSEL */
/* initialise the MMC card into SPI mode by sending 80 clks on */
/* Use MMCRDData as a temporary buffer for SPI_Send() */
for(i=0; i<10; i++)
{
MMCRDData[i] = 0xFF;
}
SPI_Send( MMCRDData, 10 );
IOCLR0 = SPI_SEL; /* clear SPI SSEL */
/* send CMD0(RESET or GO_IDLE_STATE) command, all the arguments
are 0x00 for the reset command, precalculated checksum */
MMCCmd[0] = 0x40;
MMCCmd[1] = 0x00;
MMCCmd[2] = 0x00;
MMCCmd[3] = 0x00;
MMCCmd[4] = 0x00;
MMCCmd[5] = 0x95;
SPI_Send( MMCCmd, MMC_CMD_SIZE );
/* if = 1 then there was a timeout waiting for 0x01 from the MMC */
if( mmc_response(0x01) == 1 )
{
MMCStatus = IDLE_STATE_TIMEOUT;
IOSET0 = SPI_SEL; /* set SPI SSEL */
return MMCStatus;
}
/* Send some dummy clocks after GO_IDLE_STATE */
IOSET0 = SPI_SEL; /* set SPI SSEL */
SPI_ReceiveByte();
IOCLR0 = SPI_SEL; /* clear SPI SSEL */
/* must keep sending command until zero response ia back. */
i = MAX_TIMEOUT;
do
{
/* send mmc CMD1(SEND_OP_COND) to bring out of idle state */
/* all the arguments are 0x00 for command one */
MMCCmd[0] = 0x41;
MMCCmd[1] = 0x00;
MMCCmd[2] = 0x00;
MMCCmd[3] = 0x00;
MMCCmd[4] = 0x00;
/* checksum is no longer required but we always send 0xFF */
MMCCmd[5] = 0xFF;
SPI_Send( MMCCmd, MMC_CMD_SIZE );
i--;
} while ( (mmc_response(0x00) != 0) && (i>0) );
/* timeout waiting for 0x00 from the MMC */
if ( i == 0 )
{
MMCStatus = OP_COND_TIMEOUT;
IOSET0 = SPI_SEL; /* set SPI SSEL */
return MMCStatus;
}
/* Send some dummy clocks after SEND_OP_COND */
IOSET0 = SPI_SEL; /* set SPI SSEL */
SPI_ReceiveByte();
IOCLR0 = SPI_SEL; /* clear SPI SSEL */
/* send MMC CMD16(SET_BLOCKLEN) to set the block length */
MMCCmd[0] = 0x50;
MMCCmd[1] = 0x00; /* 4 bytes from here is the block length */
/* LSB is first */
/* 00 00 00 10 set to 16 bytes */
/* 00 00 02 00 set to 512 bytes */
MMCCmd[2] = 0x00;
/* high block length bits - 512 bytes */
MMCCmd[3] = 0x02;
/* low block length bits */
MMCCmd[4] = 0x00;
/* checksum is no longer required but we always send 0xFF */
MMCCmd[5] = 0xFF;
SPI_Send( MMCCmd, MMC_CMD_SIZE );
if( (mmc_response(0x00))==1 )
{
MMCStatus = SET_BLOCKLEN_TIMEOUT;
IOSET0 = SPI_SEL; /* set SPI SSEL */
return MMCStatus;
}
IOSET0 = SPI_SEL; /* set SPI SSEL */
SPI_ReceiveByte();
return
}