620
11054A–ATARM–27-Jul-11
SAM9X25
–Enable Channel x, writing one to DMAC_CHER[x]. The DMAC is ready and
waiting for request.
8.
Wait for XFRDONE in HSMCI_SR register.
34.8.6.2
Block Length is Not Multiple of 4 and Padding Not Used (ROPT field in HSMCI_DMA register set to 0)
In the previous DMA transfer flow (block length multiple of 4), the DMA controller is configured to
use only WORD AHB access. When the block length is no longer a multiple of 4 this is no longer
true. The DMA controller is programmed to copy exactly the block length number of bytes using
2 transfer descriptors.
1.
Use the previous step until READ_SINGLE_BLOCK then
2.
Program the DMA controller to use a two descriptors linked list.
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 for the first descriptor. This descriptor
will be word oriented. This descriptor is referred to as LLI_W, standing for LLI word
oriented transfer.
d.
The LLI_W.DMAC_SADDRx field in memory must be set with the starting address
of the HSMCI_FIFO address.
e.
The LLI_W.DMAC_DADDRx field in the memory must be word aligned.
f.
Program LLI_W.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
block_length/4.
If BTSIZE is zero, this descriptor is
skipped later.
g.
Program LLI_W.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 zero. (descriptor fetch is enabled for the SRC)
–DST_DSCR is set to one. (descriptor fetch is disabled for the DST)
–DIF and SIF are set with their respective layer ID. If SIF is different from DIF, DMA
controller is able to prefetch data and write HSMCI simultaneously.
h.
Program LLI_W.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 meaning that address 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.DMAC_DSCRx with the address of LLI_B descriptor. And set
DSCRx_IF to the AHB Layer ID. This operation actually links the Word oriented
Содержание SAM9X25
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