ADSP-BF537 Blackfin Processor Hardware Reference
5-59
Direct Memory Access
transfer, which might overwrite or re-read the first buffer location
before it is processed by software. This scheme may be workable if
the system design guarantees that the data repeat period is longer
than the interrupt latency under all circumstances.
• 2D, interrupt-driven (double buffering)—the DMA buffer is parti-
tioned into two or more sub-buffers, and interrupts are selected
(set
DI_SEL = 1
in
DMAx_CONFIG
) to be signaled at the completion of
each DMA inner loop. In this way, a traditional double buffer or
“ping-pong” scheme could be implemented.
For example, two 512-word sub-buffers inside a 1K word buffer
could be used to receive 16-bit peripheral data with these settings:
DMAx_START_ADDR =
buffer base address
DMAx_CONFIG = 0x10D7
(
FLOW = 1
,
DI_EN = 1
,
DI_SEL = 1
,
DMA2D = 1
,
WDSIZE = 01
,
WNR = 1
,
DMAEN = 1
)
DMAx_X_COUNT = 512
DMAx_X_MODIFY = 2
for 16-bit data
DMAx_Y_COUNT = 2
for two sub-buffers
DMAx_Y_MODIFY = 2
, same as
DMAx_X_MODIFY
for contigu-
ous sub-buffers
• 2D, polled—if interrupt overhead is unacceptable but the loose
synchronization of address/count register polling is acceptable, a
2D multibuffer synchronization scheme may be used. For example,
assume receive data needs to be processed in packets of sixteen
32-bit elements. A four-part 2D DMA buffer can be allocated
where each of the four sub-buffers can hold one packet with these
settings:
DMAx_START_ADDR =
buffer base address
DMAx_CONFIG = 0x101B
(
FLOW = 1
,
DI_EN = 0
,
DMA2D = 1
,
WDSIZE = 10
,
WNR = 1
,
DMAEN = 1
)
DMAx_X_COUNT = 16
DMAx_X_MODIFY = 4
for 32-bit data
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 ...