
ADSP-BF59x Blackfin Processor Hardware Reference
5-11
Direct Memory Access
Stop Mode
In stop mode, the DMA operation is executed only once. When started,
the DMA channel transfers the desired number of data words and stops
itself when the transfer is complete. If the DMA channel is no longer used,
software should clear the
DMAEN
enable bit to disable the otherwise paused
channel. Stop mode is entered if the
FLOW
bit field in the DMA channel’s
DMAx_CONFIG
register is 0. The
NDSIZE
field must always be 0 in this mode.
For receive (memory write) operation, the
DMA_RUN
bit functions almost
the same as the inverted
DMA_DONE
bit. For transmit (memory read) opera-
tion, however, the two bits have different timing. Refer to the description
of the
SYNC
bit in the
DMAx_CONFIG
register for details.
Autobuffer Mode
In autobuffer mode, the DMA operates repeatedly in a circular manner. If
all data words have been transferred, the address pointer
DMAx_CURR_ADDR
is reloaded automatically by the
DMAx_START_ADDR
value. An interrupt may
also be generated.
Autobuffer mode is entered if the
FLOW
field in the
DMAx_CONFIG
register
is 1. The
NDSIZE
bit must be 0 in autobuffer mode.
Two-Dimensional DMA Operation
Register-based and descriptor-based DMA can operate in one-dimensional
mode or two-dimensional mode.
In two-dimensional (2-D) mode, the
DMAx_X_COUNT
register is accompa-
nied by the
DMAx_Y_COUNT
register, supporting arbitrary row and column
sizes up to 64K × 64K elements, as well as arbitrary
DMAx_X_MODIFY
and
DMAx_Y_MODIFY
values up to ±32K bytes. Furthermore,
DMAx_Y_MODIFY
can
be negative, allowing implementation of interleaved datastreams. The
DMAx_X_COUNT
and
DMAx_Y_COUNT
values specify the row and column sizes,
where
DMAx_X_COUNT
must be 2 or greater.
Содержание ADSP-BF59x Blackfin
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