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Programming Examples
5-118
ADSP-BF537 Blackfin Processor Hardware Reference
memory DMA. It does not gate requests to the source channel at all.
Thus, as soon as the source channel is enabled it starts filling the DMA
FIFO immediately. In 16-bit DMA mode this results in eight read strobes
on the EBIU even before the first DMAR1 event has been detected. In
other words, the transferred data and the DMAR1 strobes are eight posi-
tions off. The example in
delays processing until eight
DMAR1 requests have been received. Note that doing so the transmitter is
required to add eight trailing dummy writes after all data words have been
sent. This is because the transmit channel still has to drain the DMA
FIFO.
Listing 5-9. HMDMA With Delayed Processing
/* wait for eight requests */
p1.l = lo(HMDMA1_ECOUNT);
r0 = 7 (z);
initial_requests:
r1 = w[p1] (z);
CC = r1 < r0;
if CC jump initial_requests;
/* disable and reenable to clear edge count */
p1.l = lo(HMDMA1_CONTROL);
r0.l = 0;
w[p1] = r0;
w[p1] = r2;
If the polling operation as shown in
is too expensive, an inter-
rupt version of it can be implemented by using the HMDMA overflow
feature. Set the
HMDMAx_OVERFLOW
register to eight temporarily.
Содержание Blackfin ADSP-BF537
Страница 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...