Altera Embedded Peripherals IP Manual de usuario Pagina 205

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Byte Offset
Field Names
31 2
4
23 16 15 8 7 0
base + 4 Reserved
base + 8 destination
base +
12
Reserved
base +
16
next_desc_ptr
base +
20
Reserved
base +
24
Reserved bytes_to_transfer
base +
28
desc_control desc_status actual_bytes_
transferred
Table 21-10: DMA Descriptor Field Description
Field Name Access Description
source R/W Specifies the address of data to be read. This address is
set to 0 if the input interface is an Avalon-ST interface.
destination R/W Specifies the address to which data should be written.
This address is set to 0 if the output interface is an
Avalon-ST interface.
next_desc_ptr R/W Specifies the address of the next descriptor in the linked
list.
bytes_to_transfer R/W Specifies the number of bytes to transfer. If this field is
0, the SG-DMA controller core continues transferring
data until it encounters an EOP.
read_ R/W Specifies the burst length in bytes for a burst read from
Avalon devices (memory).
write_ R/W Specifies the burst length in bytes for a burst write to
Avalon devices (memory).
actual_bytes_
transferred
R Specifies the number of bytes that are successfully
transferred by the core. This field is updated after the
core processes a descriptor.
desc_status R/W This field is updated after the core processes a
descriptor. See DESC_STATUS Bit Map for the bit
map of this field.
desc_control R/W Specifies the behavior of the core. This field is updated
after the core processes a descriptor. See the DESC_
CONTROL Bit Map table for descriptions of each bit.
21-14
DMA Descriptors
UG-01085
2014.24.07
Altera Corporation
Scatter-Gather DMA Controller Core
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