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ADSP-BF537 Blackfin Processor Hardware Reference
5-11
Direct Memory Access
To start an MDMA transfer operation, the MMRs for the source and des-
tination channels are written, each in a manner similar to peripheral
DMA.
L
Note the
DMAx_CONFIG
register for the source channel must be writ-
ten before the
DMAx_CONFIG
register for the destination channel.
Handshaked Memory DMA Mode
Handshaked operation applies only to memory DMA channels.
Normally, memory DMA transfers are performed at maximum speed.
Once started, data is transferred in a continuous manner until either the
data count expires or the MDMA is stopped. In handshake mode, the
MDMA does not transfer data automatically when enabled; it waits for an
external trigger on the MDMA request input signals. The DMAR0 input
is associated with MDMA0 and the DMAR1 input with MDMA1. Once
a trigger event is detected, a programmable portion of data is transferred
and then the MDMA stalls again and waits for the next trigger.
Handshake operation is not only useful to control the timing of mem-
ory-to-memory transfers, it also enables the MDMA to operate with
asynchronous FIFO-style devices connected to the EBIU port. The Black-
fin processor acknowledges a DMA request by a proper number of read or
write operations. It is up to the device connected to any of the
MSx
strobes
to deassert or pulse the request signal and to decrement the number of
pending requests accordingly.
Depending on HMDMA operating mode, an external DMA request may
trigger individual data word transfers or block transfers. A block can con-
sist of up to 65535 data words. For best throughput, DMA requests can
be pipelined. The HMDMA controllers feature a request counter to
decouple request timing from the data transfers.
See
“Handshaked Memory DMA Operation” on page 5-40
for a func-
tional description.
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 ...
Страница 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
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 ...