SPI Registers
10-38
ADSP-2126x SHARC Processor Hardware Reference
SPI Transmit Data Buffer Register (TXSPI)
The Transmit Data Buffer register (
TXSPI
) is a 32-bit read-write (RW)
register. Data is loaded into this register before being transmitted. Just
prior to the beginning of a data transfer, the data in
TXSPI
is loaded into
the Transmit Shift Data (
SFDR
) register. A normal core read of
TXSPI
can
be done at any time and does not interfere with, or initiate, SPI transfers.
With DMA enabled for transmit operations, the IOP loads data into this
register. Core writes to
TXSPI
should not be made to prevent corrupting
the DMA data to be transmitted.
With DMA enabled for receive operations, the contents of the
TXSPI
regis-
ter are repeatedly transmitted. A normal core write to
TXSPI
is permitted
in this mode, and this data is transmitted. If the Send Zeroes Control bit
(
SENDZ
) is set,
TXSPI
resets once the data is transferred from
TX
to
TXSR
.
If multiple writes to
TXSPI
occur while a transfer is already in progress,
only the last data written is transmitted. None of the intermediate values
written to
TXSPI
are transmitted. Multiple writes to
TXSPI
are possible but
not recommended. To avoid overwriting data, be sure to poll the
TXS
bit
before writing to
TXSPI
.
To prevent transmit collision errors, ensure that the program writes
to the
TXSPI
register before the load to the Shift register occurs by
writing to
TXSPI
whenever
TXS
is cleared. Programs should refrain
from writing to
TXSPI
when
TXS
is set. For slave mode, data should
exist in
TXSPI
before the first SPI clock edge (or negative edge of
device select) occurs.
The
TXCOL
bit can be set when there is a
TUNF
condition and there
are attempts to write to the
TXSPI
register. In this case,
TXS
is not
set and the program wants to send new data. To ensure that
TXSPI
is written into before the next load to a Shift register occurs, write
to the
TXSPI
register as soon as the
SPIF
bit (bit 0 in the
SPISTAT
register) goes from one to zero.
Summary of Contents for ADSP-21261 SHARC
Page 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Page 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Page 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Page 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Page 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Page 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Page 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Page 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Page 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Page 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Page 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Page 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...