MMC/SD Driver (1)

1. SD card command

 

 

Static int mmc_test_set_blksize (struct mmc_test_card * test, unsigned size)
{
Struct mmc_command cmd;
Int ret;

Cmd. opcode = mmc_set_blocklen; // command
Cmd. Arg = size; // Parameter
Cmd. Flags = mmc_rsp_r1 | mmc_1__ac; // command type
Ret = mmc_wait_for_cmd (test-> card-> host, & cmd, 0 );
If (RET)
Return ret;

Return 0;
}

 

Command type ):

 

 

SPI mode & SD mode:

The SD card wakes up in the SD bus mode. It will enter SPI mode if the CS signal is asserted (negative) during the switching tion of the reset command (Limit 0 ).

The default command structure/protocol for Spi mode is that CRC checking is disabled. since the card powers up in SD bus mode, limit 0 must be followed by a valid CRC byte (even though the command is sent using the SPI structure ). once in SPI mode, CRCs are disabled by default.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2. SD reference program

// SD card write command // SD send command <br/> uint8 mmc_sd_sendcommand (uint8 cmd, uint32 Arg) <br/>{< br/> uint8 R1; <br/> uint8 retry = 0; </P> <p> spi_writebyte (0xff); <br/> spi_writebyte (0xff); <br/> spi_writebyte (0xff ); <br/> spi_writebyte (0xff); <br/> spi_writebyte (0xff); <br/> spi_writebyte (0xff); </P> <p> spi_cs_assert (); </P> <p> spi_writebyte (CMD | 0x40); // write commands separately // send command <br/> spi_writebyte (Arg> 24 ); <br/> spi_writeby Te (Arg> 16); <br/> spi_writebyte (Arg> 8); <br/> spi_writebyte (ARG); <br/> spi_writebyte (0x95 ); </P> <p> while (r1 = spi_writebyte (0xff) = 0xff) // wait for a response, // Wait response <br/> If (retry ++> 100) break; // exit upon timeout // time out error </P> <p> spi_cs_deassert (); </P> <p> return R1; // return status value // return state <br/>}</P> <p> // SD card reset // reset SD card (software) <br/> uint8 mmc_sd_reset (void) <br/>{< br/> uint8 I; <br/> uint8 retry; <br/> UI Nt8 R1 = 0; <br/> retry = 0; <br/> spi_low (); </P> <p> DO <br/> {<br/> for (I = 0; I <100; I ++) spi_writebyte (0xff ); <br/> R1 = mmc_sd_sendcommand (0, 0); // send the idle command <br/> retry ++; <br/> If (retry> 10) return 1; // exit upon timeout // time out <br/>} while (R1! = 0x01); </P> <p> retry = 0; <br/> DO <br/> {<br/> R1 = mmc_sd_sendcommand (1, 0 ); // send the active command <br/> retry ++; <br/> If (retry> 100) return 1; // exit upon timeout // time out <br/>} while (R1); <br/> spi_high (); <br/> R1 = mmc_sd_sendcommand (59, 0 ); // disable CRC </P> <p> R1 = mmc_sd_sendcommand (16,512 ); // set the slice size to 512 // set sector size to 512 <br/> return 0; // normal return <br/>}

 

 

3. processor flowchart on how to identify sdio, SD, and MMC (Linux)

 

 

Nanjing