ADSP-21368 SHARC Processor Hardware Reference 6-23
Serial Peripheral Interface Ports
3. Wait for the SPI shift register to finish transferring the last word.
This is done when the
SPIF bit (bit 0 of the SPISTATx registers),
becomes one.
4. Disable the SPI ports by setting the SPIEN bit (bit 0 of the SPICTLx
registers), to zero.
Switching From Transmit To Receive DMA
The following sequence details the steps for switching from transmit to
receive DMA.
With disabling the SPI:
1. Write 0x00 to the SPICTLx registers to disable SPI. Disabling the
SPI also clears the RXSPIx/TXSPIx registers and the buffer status.
2. Disable DMA by writing 0x00 to the SPIDMACx registers.
3. Clear all errors by writing to the W1C-type bits in the SPISTATx
registers. This ensures that no interrupts occur due to errors from a
previous DMA operation.
4. Reconfigure the SPICTLx registers and enable the SPI ports.
5. Configure DMA by writing to the DMA parameter registers and
enable DMA.
Without disabling the SPI:
1. Clear
RXSPIx/TXSPIx and the buffer status without disabling SPI.
This can be done by ORing 0xC0000 with the present value in the
SPICTLx registers. For example, programs can use the RXFLSH and
TXFLSH bits to clear TXSPIx/RXSPIx and the buffer status.
2. Disable DMA by writing 0x00 to the SPIDMAC register.
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