ADSP-BF50x Blackfin Processor Hardware Reference
7-25
Direct Memory Access
• If
FLOW
= any value but 0 (Stop), the DMA controller begins the
next work unit for that channel, which must contend with other
channels for priority on the memory buses. On the first memory
transfer of the new work unit, the DMA controller updates the cur-
rent registers from the start registers:
DMAx_CURR_ADDR
loaded from
DMAx_START_ADDR
DMAx_CURR_X_COUNT
loaded from
DMAx_X_COUNT
DMAx_CURR_Y_COUNT
loaded from
DMAx_Y_COUNT
The
DFETCH
bit in the
DMAx_IRQ_STATUS
register is then cleared,
after which the DMA transfer begins again, as shown in
Figure 7-2
on page 7-20
.
Work Unit Transitions
Transitions from one work unit to the next are controlled by the
SYNC
bit
in the
DMAx_CONFIG
register of the work units. In general, continuous tran-
sitions have lower latency at the cost of restrictions on changes of data
format or addressed memory space in the two work units. These latency
gains and data restrictions arise from the way the DMA FIFO pipeline is
handled while the next descriptor is fetched. In continuous transitions
(
SYNC
= 0), the DMA FIFO pipeline continues to transfer data to and
from the peripheral or destination memory during the descriptor fetch
and/or when the DMA channel is paused between descriptor chains.
Synchronized transitions (
SYNC
= 1), on the other hand, provide better
real-time synchronization of interrupts with peripheral state and greater
flexibility in the data formats and memory spaces of the two work units, at
the cost of higher latency in the transition. In synchronized transitions,
the DMA FIFO pipeline is drained to the destination or flushed (RX data
discarded) between work units.
Work unit transitions for MDMA streams are controlled by the
SYNC
bit of the MDMA source channel’s
DMAx_CONFIG
register. The
SYNC
bit of the MDMA destination channel is reserved and must be
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 ...