Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK データシート

 687

SAM9M10 [DATASHEET]

6355F–ATARM–12-Mar-13

a.

Read the channel Register to choose an available (disabled) channel.

b.

Clear any pending interrupts on the channel from the previous DMA transfer by reading the 
DMAC_EBCISR register.

c.

Program the channel registers in the Memory with the first descriptor. This descriptor will be word ori-
ented. This descriptor is referred to as LLI_W(n), standing for LLI word oriented transfer for block 

.

d.

The LLI_W(n).DMAC_SADDRx field in memory must be set with the starting address of the 
HSMCI_FIFO address.

e.

The LLI_W(n).DMAC_DADDRx field in the memory must be word aligned.

f.

Program LLI_W(n).DMAC_CTRLAx with the following field’s values:

–DST_WIDTH is set to WORD

–SRC_WIDTH is set to WORD

–SCSIZE must be set according to the value of HSMCI_DMA, CHKSIZE field.

–BTSIZE is programmed with 

g.

Program LLI_W(n).DMAC_CTRLBx with the following field’s values:

–DST_INCR is set to INCR.

–SRC_INCR is set to INCR.

–FC field is programmed with peripheral to memory flow control mode.

–SRC_DSCR is set to 0 (descriptor fetch is enabled for the SRC).

–DST_DSCR is set to TRUE (descriptor fetch is disabled for the DST).

–DIF and SIF are set with their respective layer ID. If SIF is different from DIF, the DMA Controller is 

able to prefetch data and write HSMCI simultaneously.

h.

Program LLI_W(n).DMAC_CFGx register for channel x with the following field’s values:

–FIFOCFG defines the watermark of the DMA channel FIFO.

–DST_REP is set to zero. Addresses are contiguous.

–SRC_H2SEL is set to true to enable hardware handshaking on the destination.

–SRC_PER is programmed with the hardware handshaking ID of the targeted HSMCI Host 

Controller.

i.

Program LLI_W(n).DMAC_DSCRx with the address of LLI_W(n+1) descriptor. And set the DSCRx_IF 
to the AHB Layer ID. This operation actually links descriptors together. If LLI_W(n) is the last descrip-
tor then LLI_W(n).DMAC_DSCRx points to 0.

j.

Program DMAC_CTRLBx register for channel x with 0. its content is updated with the LLI Fetch 
operation.

k.

Program DMAC_DSCRx register for channel x with the address of LLI_W(0).

l.

Enable Channel x writing one to DMAC_CHER[x]. The DMA is ready and waiting for request.

8.

Poll CBTC[x] bit in the DMAC_EBCISR Register.

9.

If a new list of buffer shall be transferred repeat step 6. Check and handle HSMCI errors.

10. Poll FIFOEMPTY field in the HSMCI_SR. 

11. Send The STOP_TRANSMISSION command writing the HSMCI_ARG then the HSMCI_CMDR.

12. Wait for XFRDONE in HSMCI_SR register.

Two DMA Transfer descriptors are used to perform the HSMCI block transfer.

1.

Use the previous step to configure the HSMCI to perform a READ_MULTIPLE_BLOCK command.

2.

Issue a READ_MULTIPLE_BLOCK command.

3.

Program the DMA Controller to use a list of descriptors.