Description of Operation
10-14
ADSP-BF537 Blackfin Processor Hardware Reference
If multiple writes to
SPI_TDBR
occur while a transfer is already in progress,
only the last data written is transmitted. None of the intermediate values
written to
SPI_TDBR
are transmitted. Multiple writes to
SPI_TDBR
are pos-
sible, but not recommended.
SPI Receive Data Buffer
The
SPI_RDBR
register is a 16-bit read-only register. At the end of a data
transfer, the data in the shift register is loaded into
SPI_RDBR
. During a
DMA receive operation, the data in
SPI_RDBR
is automatically read by the
DMA. When
SPI_RDBR
is read via software, the
RXS
bit is cleared and an
SPI transfer may be initiated (if
TIMOD = 00
).
The
SPI_SHADOW
register has been provided for use in debugging software.
This register is at a different address than the receive data buffer,
SPI_RDBR
, but its contents are identical to that of
SPI_RDBR
. When a soft-
ware read of
SPI_RDBR
occurs, the
RXS
bit in
SPI_STAT
is cleared and an
SPI transfer may be initiated (if
TIMOD = 00 in SPI_CTL
). No such hard-
ware action occurs when the
SPI_SHADOW
register is read. The
SPI_SHADOW
register is read-only.
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. These combinations are selected using the
CPOL
and
CPHA
bits in
SPI_CTL
.
The figures
“SPI Transfer Protocol for CPHA = 0” on page 10-16
“SPI Transfer Protocol for CPHA = 1” on page 10-16
demonstrate the
two basic transfer formats as defined by the
CPHA
bit. Two waveforms are
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 ...