Programming Model
10-34
ADSP-BF537 Blackfin Processor Hardware Reference
5. In receive mode, as long as there is data in the SPI DMA FIFO
(FIFO not empty), the SPI slave continues to request a DMA write
to memory. The DMA engine continues to read a word from the
SPI DMA FIFO and writes to memory until the SPI DMA word
count register transitions from 1 to 0. The SPI slave continues
receiving words on active
SCK
edges as long as the slave select input
is active.
In transmit mode, as long as there is room in the SPI DMA FIFO
(FIFO not full), the SPI slave continues to request a DMA read
from memory. The DMA engine continues to read a word from
memory and write to the SPI DMA FIFO until the SPI DMA word
count register transitions from 1 to 0. The SPI slave continues
transmitting words on active
SCK
edges as long as the slave select
input is active.
See
For receive DMA operations, if the DMA engine is unable to keep up with
the receive datastream, the receive buffer operates according to the state of
the
GM
bit. If
GM = 1
and the DMA FIFO is full, the device continues to
receive new data from the
MOSI
pin, overwriting the older data in the
SPI_RDBR
register. If
GM = 0
and the DMA FIFO is full, the incoming data
is discarded, and the
SPI_RDBR
register is not updated. While performing
receive DMA, the transmit buffer is assumed to be empty and
TXE
is set. If
SZ = 1
, the device repeatedly transmits 0s on the
MISO
pin. If
SZ = 0
, it
repeatedly transmits the contents of the
SPI_TDBR
register. The
TXE
under-
run condition cannot generate an error interrupt in this mode.
For transmit DMA operations, if the DMA engine is unable to keep up
with the transmit stream, the transmit port operates according to the state
of the
SZ
bit. If
SZ = 1
and the DMA FIFO is empty, the device repeat-
edly transmits 0s on the
MISO
pin. If
SZ = 0
and the DMA FIFO is empty,
it repeatedly transmits the last word it transmitted before the DMA buffer
became empty. All aspects of SPI receive operation should be ignored
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 ...