Analog Devices SHARC ADSP-214 Series Hardware Reference Manual page 639

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DMA Chaining

The serial peripheral interfaces support both single and chained DMA.

However, unlike the serial ports, programs cannot insert a TCB in an

active chain.

For more information, see "SPI TCB" on page 2-14.

Configuring and starting chained DMA transfers over the SPI port is the

same as for the serial ports, with one exception. Contrary to SPORT

DMA chaining, (where the first DMA in the chain is configured by the

first TCB), for SPI DMA chaining, the first DMA is not initialized by a

TCB. Instead, the first DMA in the chain must be loaded into the SPI

parameter registers (

chain pointer registers (

second DMA in the sequence.

Writing an address to the

chained DMA sequence unless the

the SPI port is enabled, and SPI DMA chaining is enabled.

DMA Transfer Count

When the SPI is configured for receive/transmit DMA, the number of

words configured in the DMA count register should match the actual data

transmitted. When the SPI DMA is used, the internal DMA request is

generated for a DMA count of four. In case the count is less than four, one

DMA request is generated for all the bytes.

For example, when a DMA count of 16 is programmed, four DMA

requests are generated (that is, four groups of four). For a DMA count of

18, five DMA requests are generated (four groups of four and one group

of two). In case the SPI DMA is programmed with a value more than the

actual data transmitted, some bytes may not be received by the SPI DMA

due to the condition for generating the DMA request.

ADSP-214xx SHARC Processor Hardware Reference

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Serial Peripheral Interface Ports

) point to a TCB that describes the

registers are initialized, SPI DMA is enabled,

, registers does not begin a

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