Description of Operation
18-12
ADSP-BF50x Blackfin Processor Hardware Reference
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 gets set, the
last word has been transferred.
The four-word FIFO is cleared when the SPI port is disabled.
Description of Operation
The following sections describe the operation of the SPI.
SPI Transfer Protocols
The SPI protocol supports four different combinations of serial clock
phase and polarity (SPI modes 0, 1, 2, 3). These combinations are selected
using the
CPOL
and
CPHA
bits in
SPI_CTL
as shown in
Figure 18-5
.
Figure 18-6 on page 18-14
and
Figure 18-7 on page 18-14
demonstrate
the two basic transfer formats as defined by the
CPHA
bit. Two waveforms
are shown for
SCK
—one for
CPOL
= 0 and the other for
CPOL
= 1. The dia-
grams may be interpreted as master or slave timing diagrams since the
SCK
,
MISO
, and
MOSI
pins are directly connected between the master and the
slave. The
MISO
signal is the output from the slave (slave transmission),
and the
MOSI
signal is the output from the master (master transmission).
The
SCK
signal is generated by the master, and the
SPISS
signal is the slave
device select input to the slave from the master. The diagrams represent an
8-bit transfer (
SIZE
= 0) with the most significant bit (MSB) first
(
LSBF
= 0). Any combination of the
SIZE
and
LSBF
bits of
SPI_CTL
is
allowed. For example, a 16-bit transfer with the least significant bit (LSB)
first is another possible configuration.
Содержание EZ-KIT Lite ADSP-BF506F
Страница 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 132: ...Unique Information for the ADSP BF50x Processor 4 22 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 342: ...Unique Information for the ADSP BF50x Processor 7 106 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 484: ...Unique Information for the ADSP BF50x Processor 10 60 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 493: ...ADSP BF50x Blackfin Processor Hardware Reference 11 9 Core Timer Unique Information for the ADSP BF50x Processor None ...
Страница 494: ...Unique Information for the ADSP BF50x Processor 11 10 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 506: ...Unique Information for the ADSP BF50x Processor 12 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 544: ...Unique Information for the ADSP BF50x Processor 13 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 712: ...Unique Information for the ADSP BF50x Processor 16 62 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 972: ...Unique Information for the ADSP BF50x Processor 20 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...