ADSP-BF537 Blackfin Processor Hardware Reference
10-13
SPI Compatible Port Controllers
When configured as a receive channel, what is transmitted is irrelevant. A
16-bit by four-word FIFO (without burst capability) is included to
improve throughput on the DAB.
L
When using DMA for SPI transmit, the
DMA_DONE
interrupt signi-
fies that the DMA FIFO is empty. However, at this point there
may still be data in the SPI DMA FIFO waiting to be transmitted.
Therefore, software needs to poll
TXS
in the
SPI_STAT
register until
it goes low for two successive reads, at which point the SPI DMA
FIFO will be empty. When the
SPIF
bit subsequently goes low, the
last word has been transferred and the SPI can be disabled or
enabled for another mode.
The four-word FIFO is cleared when the SPI port is disabled.
SPI Transmit Data Buffer
The
SPI_TDBR
register is a 16-bit read-write register. Data is loaded into
this register before being transmitted. Just prior to the beginning of a data
transfer, the data in
SPI_TDBR
is loaded into the
SFDR
register. A read of
SPI_TDBR
can occur at any time and does not interfere with or initiate SPI
transfers.
When the DMA is enabled for transmit operation, the DMA engine loads
data into this register for transmission just prior to the beginning of a data
transfer. A write to
SPI_TDBR
should not occur in this mode because this
data will overwrite the DMA data to be transmitted.
When the DMA is enabled for receive operation, the contents of
SPI_TDBR
are repeatedly transmitted. A write to
SPI_TDBR
is permitted in this mode,
and this data is transmitted.
If the
SZ
control bit in the
SPI_CTL
register is set,
SPI_TDBR
may be reset to
0 under certain circumstances.
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...