Programming Model
5-66
ADSP-BF537 Blackfin Processor Hardware Reference
The next descriptor pointer remains valid, if the DMA halts and is
restarted. As soon as the
DMA_RUN
bit clears, software can restart the DMA
and force the DMA controller to fetch the next descriptor. To accomplish
this, the software writes a value with the
DMAEN
bit set and with proper val-
ues in the
FLOW
and
NDSIZE
fields into the configuration register. The next
descriptor is fetched if
FLOW
equals
0x4
,
0x6
, or
0x7
. In this mode of opera-
tion, the
NDSIZE
field should at least span up to the
DMACFG
field to
overwrite the configuration register immediately.
One possible procedure is:
1. Write to
DMAx_NEXT_DESC_PTR
.
2. Write to
DMAx_CONFIG
with
FLOW
=
0x8
NDSIZE
>=
0xA
DI_EN
=
0
DMAEN
=
1
.
3. Automatically fetched
DMACFG
has
FLOW
=
0x0
NDSIZE
=
0x0
SYNC
=
1
(for transmitting DMAs only)
DI_EN
=
1
DMAEN
=
1
.
4. In the interrupt routine, repeat step 2. The
DMAx_NEXT_DESC_PTR
is
updated by the descriptor fetch.
L
To avoid polling of the
DMA_RUN
bit, set the
SYNC
bit in case of
memory read DMAs (DMA transmit or MDMA source).
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 ...