Programming Examples
7-102
ADSP-BF50x Blackfin Processor Hardware Reference
w[p1] = r0;
/* enable for rising edges */
p1.l = lo(HMDMA1_CONTROL);
r2.l = REP | HMDMAEN;
w[p1] = r2;
If the HMDMA is intended to copy from internal memory to external
devices, the above setup is sufficient. If, however, the data flow is from
outside the processor to internal memory, then this small issue must be
considered—the HMDMA only controls the destination channel of the
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
Listing 7-9
delays processing until eight
DMAR1 requests have been received. By 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 7-9. 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;
Summary of Contents for EZ-KIT Lite ADSP-BF506F
Page 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Page 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Page 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...