= GIET-VM / SDC Driver = 

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The [source:soft/giet_vm/giet_drivers/sdc_driver.c sdc_driver.c] and [source:soft/giet_vm/giet_drivers/sdc_driver.h sdc_driver.h] files define the SDC driver. 

This component is a single channel, block oriented, external mass storage peripheral, implemented on a SD card. 

The SDC driver uses the lower level SPI driver to access the SD card.

It is called by the generic FAT handler when the USE_IOC_SPI flag is set in the hard_config.h file. 

The SEG_IOC_BASE address must be defined in the hard_config.h file.

In this implementation, the SDC peripheral is acting as a target (no DMA capability) :  the '''_sdc_access()''' function is blocking until the transfer is fully completed, and does not use any interrupt to signal completion, whatever the requested mode. 

WARNING : Write transfers (from memory to SD card) are not supported yet.

 == __Access functions__ ==

 === unsigned int '''_sdc_init'''() ===
This function initializes the SPI controller and call sdc_open to initialize  the SD card.
Returns 0 if success, >0 if failure

 === unsigned int '''_sdc_access'''( unsigned int use_irq  ,  unsigned int to_mem  ,  unsigned int lba,  unsigned long long buffer,  unsigned int count ) ===
Transfer data from the SD card to a memory buffer. 
 * '''use_irq''' : unused, access is always synchronous.
 * '''to_mem''' : must be non zero as write transfer are not supported yet.
 * '''lba'''  : first block index on the SD card.
 * '''buffer''' : physical base address of the memory buffer 
 * '''count''' : number of blocks to be transfered.
Returns 0 if success, > 0 if error.