Setting Up And Starting The Chain - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

IOP/Core Interaction Options
cannot be interrupted by a higher priority channel. For a list of DMA
channels in priority order, see

Setting Up and Starting the Chain

To set up and initiate a chain of DMA operations, use these steps:
1. Clear the chain pointer register first before enabling chaining.
2. Set up all TCBs in internal memory.
3. Write to the appropriate DMA control register, setting the DMA
enable bit to one and the chaining enable bit to one.
4. Write the address containing the index register value of the first
TCB to the chain pointer register, which starts the chain.
The I/O processor responds by autoinitializing the first DMA parameter
registers with the values from the first TCB, and then starts the first data
transfer.
Setting Up and Starting Chained DMA over the SPI
Configuring and starting chained DMA transfers over the SPI port is the
same as for the serial port, 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 (
IISPI
points to a TCB that describes the second DMA in the sequence.

Writing an address to the
DMA sequence unless
DMA is enabled, the SPI port is enabled, and SPI DMA chaining is
enabled.
7-14
Table 7-5 on page
, , ), and the chain pointer register (
IMSPI CSPI
CPSPI
IISPI
ADSP-2126x SHARC Processor Hardware Reference
7-28.
register does not begin a chained
, , and
IMSPI CSPI
)
CPSPI
are initialized, SPI