ADSP-2126x SHARC Processor Hardware Reference
10-47
Serial Peripheral Interface Port
service another DMA channel (or for another reason), the
SPICLK
stalls
until data is written into the
TXSPI
register. All aspects of SPI receive
operation should be ignored. The data in the
RXSPI
register is not
intended to be used, and the
RXS
(bits 28–27 and 31–30 in the
SPICTLx
registers) and
SPISTAT
bits (bits 26 and 29) should be ignored. The
ROVF
overrun condition cannot generate an error interrupt in this mode.
If the DMA engine cannot keep up with the receive data stream during
receive operations, then
SPICLK
stalls until data is read from
RXSPI
. While
performing a receive DMA, the processor core assumes the transmit buffer
is empty. If
SENDZ
= 1, the device repeatedly transmits 0s. If
SENDZ
= 0, it
repeatedly transmits the contents of the
TXSPI
register. The
TUNF
underrun
condition cannot generate an error interrupt in this mode.
A master SPI DMA sequence may involve back-to-back transmission
and/or reception of multiple chained DMA transfers. The SPI controller
supports such a sequence with minimal processor core interaction.
Slave Mode DMA Transfers
A slave mode DMA transfer occurs when the SPI port is enabled and con-
figured in slave mode, and DMA is enabled. When the
SPIDS
signal
transitions to the active-low state or when the first active edge of
SPICLK
is
detected, it triggers the start of a transfer.
When the SPI is configured for receive/transmit DMA, the number of
words configured in the DMA count register should match the actual data
transmitted. When the SPI DMA is used, the internal DMA request is
generated for a DMA count of four. In case the count is less than four, one
DMA request is generated for all the bytes. For example, when a DMA
count of 16 is programmed, four DMA requests are generated (that is,
four groups of four). For a DMA count of 18, five DMA requests are gen-
erated (four groups of four and one group of two). In case the SPI DMA is
programmed with a value more than the actual data transmitted, some
Содержание ADSP-21261 SHARC
Страница 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Страница 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Страница 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Страница 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Страница 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...