ADSP-BF537 Blackfin Processor Hardware Reference
5-15
Direct Memory Access
The
DMAx_X_MODIFY
value is the byte-address increment that is applied
after each transfer that decrements the
DMAx_CURR_X_COUNT
register. The
DMAx_X_MODIFY
value is not applied when the inner loop count is ended by
decrementing
DMAx_CURR_X_COUNT
from 1 to 0, except that it is applied on
the final transfer when
DMAx_CURR_Y_COUNT
is 1 and
DMAx_CURR_X_COUNT
decrements from 1 to 0.
The
DMAx_Y_MODIFY
value is the byte-address increment that is applied
after each decrement of
DMAx_CURR_Y_COUNT
. However, the
DMAx_Y_MODIFY
value is not applied to the last item in the array on which the outer loop
count (
DMAx_CURR_Y_COUNT
) also expires by decrementing from 1 to 0.
After the last transfer completes,
DMAx_CURR_Y_COUNT
=
1
,
DMAx_CURR_X_
COUNT = 0
, and
DMAx_CURR_ADDR
is equal to the last item’s address plus
DMAx_X_MODIFY
. Note if the DMA channel is programmed to refresh auto-
matically (autobuffer mode), then these registers will be loaded from
DMAx_X_COUNT
,
DMAx_Y_COUNT
, and
DMAx_START_ADDR
upon the first data
transfer.
The
DI_SEL
configuration bit enables DMA interrupt requests every time
the inner loop rolls over. If
DI_SEL
is cleared, but
DI_EN
is still set, only
one interrupt is generated after the outer loop completes.
Examples of Two-Dimensional DMA
Example 1: Retrieve a 16
×
8 block of bytes from a video frame buffer of
size (N
×
M) pixels:
DMAx_X_MODIFY = 1
DMAx_X_COUNT = 16
DMAx_Y_MODIFY = N–15 (offset from the end of one row to the start
of another)
DMAx_Y_COUNT = 8
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 ...