ADSP-214xx SHARC Processor Hardware Reference
10-47
Serial Ports
DMA Chaining
Each channel also has a DMA chaining enable bit (
SCHEN_A
and
SCHEN_B
)
in its
SPCTLx
control register.
Each SPORT DMA channel also has a chain pointer register (
CPSPxy
).
The
CPSPxy
register functions are used in chained DMA operations.
In chained DMA operations, the processor’s DMA controller automati-
cally sets up another DMA transfer when the contents of the current
buffer have been transmitted (or received). The chain pointer register
(
CPSPxy
) functions as a pointer to the next set of buffer parameters stored
in external or internal memory. The DMA controller automatically down-
loads these buffer parameters to set up the next DMA sequence. For more
information on SPORT DMA chaining, see
.
DMA chaining occurs independently for the transmit and receive channels
of each serial port. Each SPORT DMA channel has a chaining enable bit
(
SCHEN_A
or
SCHEN_B
) that when set (= 1), enables DMA chaining and
when cleared (= 0), disables DMA chaining. Writing all zeros to the
address field of the chain pointer register (
CPSPxy
) also disables chaining.
The chain pointer register should be cleared first before chaining is
enabled.
The I/O processor responds by auto-initializing the first DMA parameter
registers with the values from the first TCB, and then starts the first data
transfer.
Although the word lengths can be 3 to 32 bits, transmitting or
receiving words smaller than 7 bits at the full clock rate of the serial
port may cause incorrect operation when DMA chaining is
enabled. Chaining locks the processor’s internal I/O bus for several
cycles while the new transfer control block (TCB) parameters are
being loaded. Receive data may be lost (for example, overwritten)
during this period.
www.BDTIC.com/ADI
Содержание SHARC ADSP-214 Series
Страница 60: ...Contents lx ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 72: ...Notation Conventions lxxii ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 130: ...Programming Model 2 52 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 264: ...Programming Models 3 134 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 290: ...Programming Model 4 26 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 296: ...Programming Model 5 6 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 396: ...Effect Latency 7 28 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 520: ...Programming Model 10 62 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 656: ...Programming Model 15 40 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 714: ...Programming Model 19 10 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...