External Port DMA
3-112
ADSP-214xx SHARC Processor Hardware Reference
single reads from each TAP are shown for simplicity and block reads are
default, depending on the count specified in the
RCEP
register.
1. Writes to external memory. The number of writes is determined by
the
ICEP
register. The data is fetched from the
IIEP
register and the
IMEP
register is used as the internal modifier. The
EIEP
register
serves as the external index and is incremented by the
EMEP
register
after each write. These writes are circular buffered if circular buff-
ering is enabled.
2. In chained DMA, when the writes are complete, (
ICEP
= zero) the
EIEP
register, which serves as the write pointer of the delay line, is
written back to the internal memory location from where it was
fetched.
3. Reads from external memories. For reads, the tap list (TL) modifi-
ers are used and the number of reads is determined by the
RCEP
register. The write pointer in the
EIEP
register serves as the index
address for these reads (reads start from where writes end). The
EIEP
register, along with tap list modifiers, are used in a pre-modify
addressing mode to create the external address for the writes.
Therefore, for each read, the DMA controller fetches the external
modifier from the tap list and the reads are circular buffered (if
enabled).
External Address Calculation for Reads
Note that TL[N] is the first tap list entry in internal memory pointed to
by the tap list pointer register (
TPEP
). Tap list entries are 27-bit signed
integers. Therefore, for each read-block, the DMA state machine fetches
the offset external modifier from the tap list. The reads are circular buff-
ered if circular buffering is enabled.
The external address generation follows pre-modify addressing for
reads in delay line DMA and therefore the
EIEP
register values are
not modified. Also the
EMEP
register does not have any effect during
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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...