DMA and SSP in LPC11Uxx

[pberna]

Dear All,

The user manual of the LPC11U68 indicates that the DMA can be used with the SSP

Table 229: SSP/SPI DMA Control Register (DMACR, address

RXDMAE Receive DMA Enable. When this bit is set to one 1, DMA

for the receive FIFO is enabled, otherwise receive DMA is

disabled.

0

1 TXDMAE Transmit DMA Enable. When this bit is set to one 1, DMA

for the transmit FIFO is enabled, otherwise transmit DMA

is disabled

Can anybody clarify what are the event which trigger the DMA RX and TX requests (Start of transfers) ?

Thanks

[kerryzhou]

Hi Paolo,

    I get that the LPC11U68 SPI DMA can refer to LPC82X, so the SPI DMA question should like this:

DMA operation

A DMA request is provided for each SPI direction, and can be used in lieu of interrupts for transferring data by configuring the DMA controller appropriately, and enabling the Rx

and/or Tx DMA via the DMACR register. The DMA controller provides an acknowledgement signal that clears the related request when it completes handling that request.

The transmitter DMA request is asserted when Tx DMA is enabled and the transmitter can accept more data.

The receiver DMA request is asserted when Rx DMA is enabled and received data is available to be read.

    Besides the SPI FIFO as the DMA request, DMA trigger also can start the SPI transfer, for details, please refer to the DMA chapter about the trigger.

Wish it helps you!

If you still have question, please let me know!

Have a great day,
Jingjing

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