Operating Modes
2-32
ADSP-214xx SHARC Processor Hardware Reference
DMA Chaining
DMA data transfers can be set up as continuous or periodic. Furthermore,
these DMA transfers can be configured to run automatically using chained
DMA. With chained DMA, the attributes of a specific DMA are stored in
internal memory and are referred to as a
Transfer Control Block
or TCB.
The DMA controller loads these attributes in chains for execution. This
allows for multiple chains that are an finite or infinite.
If chaining is enabled on a DMA channel, programs should not use
polling to determine channel status as this gives inaccurate infor-
mation where the DMA appears inactive if it is sampled while the
next TCB is loading.
TCB Memory Storage
The location of the DMA parameters for the next sequence comes from
the chain pointer register that points to the next set of DMA parameters
stored in the processor’s internal memory. In chained DMA operations,
the processor automatically initializes and then begins another DMA
transfer when the current DMA transfer is complete. Each new set of
parameters is stored in a user-initialized memory buffer or TCB for a cho-
sen peripheral.
provides a brief description of the TCBs.
The size of a TCB varies and is based on the peripheral to be used:
the SPORTs, link ports and SPI require four locations, the external
port requires six to 13 locations, the accelerator five to 13 loca-
tions. Allowing different TCB sizes reduces the memory load since
only the required TCBs are allocated in internal memory.
Table 2-27. Principal TCB Allocation for a Serial Peripheral
Address
Register
Description
CPx
Chain pointer register
Chain pointer for DMA chaining
CPx + 0x1 (ICx)
Internal count register
Length of internal buffer
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Содержание SHARC ADSP-214 Series
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Страница 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
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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...