Functional Description
5-20
ADSP-BF537 Blackfin Processor Hardware Reference
the first descriptor if a descriptor array is used in an endless manner. If the
descriptor chain is not endless and the DMA is required to stop after a cer-
tain descriptor has been processed, the last descriptor is typically processed
in stop mode, that is, its
FLOW
and
NDSIZE
fields are 0, but its
DMAEN
bit is
still set.
Functional Description
The following sections provide a functional description of DMA.
DMA Operation Flow
DMA Startup
This section discusses starting DMA “from scratch.” This is similar to
starting it after it has been paused by
FLOW = 0
mode.
a
Before initiating DMA for the first time on a given channel, be
sure to initialize all parameter registers. Be especially careful to ini-
tialize the upper 16 bits of the
DMAx_NEXT_DESC_PTR
and
DMAx_
START_ADDR
registers, because they might not otherwise be accessed,
depending on the chosen
FLOW
mode of operation. Also note that
the
DMAx_X_MODIFY
and
DMAx_Y_MODIFY
are not preset to a default
value at reset.
To start DMA operation on a given channel, some or all of the DMA
parameter registers must first be written directly. At a minimum, the
DMAx_NEXT_DESC_PTR
register (or
DMAx_CURR_DESC_PTR
register in
FLOW = 4
mode) must be written at this stage, but the user may wish to write other
DMA registers that might be static throughout the course of DMA activ-
ity (for example,
DMAx_X_MODIFY
,
DMAx_Y_MODIFY
). The contents of
NDSIZE
and
FLOW
in
DMAx_CONFIG
indicate which registers, if any, are fetched from
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...