Scatter/Gather Dma; External Address Calculation - Analog Devices SHARC ADSP-214 Series Hardware Reference Manual

External Port DMA

If chaining is enabled with the
no effect, and direction is determined by the
register.

Scatter/Gather DMA

The purpose of scatter/gather DMA
Figure 3-27) is the transfer of data from/to non contiguous memory
blocks.
The scatter/gather DMA type is a fixed block size scatter/gather DMA
that relies on tap list entries in internal memory to calculate the external
address to scatter/gather the DMA. If the DMA direction is external write
( = 1) then it is a scatter DMA. If
TRAN
This mode also supports chained and circular buffer chained DMAs.
Table 3-26. External Read/Write Index Calculation
Scatter/Gather DMA
Equation
EIEP + TL[N]
EIEP + TL[N] + 1
EIEP + TL[N] + 2
...
EIEP + TL[N] + ICEP
EIEP + TL[N + 1]
EIEP + TL[N + 1] + 1

External Address Calculation

For scatter/gather DMA, the tap list modifiers are employed and the num-
ber of taps is determined by the tap list count register (
number of sequential reads (block size) from every tap is determined by
3-106
www.BDTIC.com/ADI
×
EMEP
×
EMEP
×
EMEP
×
EMEP
ADSP-214xx SHARC Processor Hardware Reference
bit set then the
OFCEN
CPDR
(Table 3-26, Figure 3-24
= 0 then it is a gather DMA.
TRAN
Result
First address for tap N
Second address for tap N
Third address for tap N
Final address for tap N
First address for tap N + 1
Second address for tap N + 1
TCEPx
bit has
TRAN
bit in the
CPEP
through
). The