ADSP-2126x SHARC Processor Hardware Reference
10-29
Serial Peripheral Interface Port
The
RXS
bit defines when the receive buffer can be read; the
TXS
bit defines
when the transmit buffer can be filled. The end of a single word transfer
occurs when the
RXS
bit is set. This indicates that a new word has just been
received and latched into the receive buffer,
RXSPI
. The
RXS
bit is set
shortly after the last sampling edge of
SPICLK
. The latency is typically a
few core clock cycles and is independent of
CPHASE
,
TIMOD
, and the baud
rate. If configured to generate an interrupt when
RXSPI
is full (
TIMOD
=
00), the interrupt becomes active one core clock cycle after
RXS
is set.
When not relying on this interrupt, the end of a transfer can be detected
by polling the
RXS
bit.
To maintain software compatibility with other SPI devices, the SPI Trans-
fer Finished bit (
SPIF
) is also available for polling. This bit may have
slightly different behavior from that of other commercially available
devices. For a slave device,
SPIF
is set at the same time as
RXS
; for a master
device,
SPIF
is set one-half of the
SPICLK
period after the last
SPICLK
edge,
regardless of
CPHASE
or
CLKPL
.
The baud rate determines when the
SPIF
bit is set. In general,
SPIF
is set
after
RXS
, but at the lowest baud rate settings (
SPIBAUD<4
). The
SPIF
bit is
set before the
RXS
bit is set, and consequently before new data has been
latched into the
RXSPI
buffer. For
SPIBAUD
= 2 or
SPIBAUD
= 3, the proces-
sor must wait for the
RXS
bit to be set (after
SPIF
is set) before reading the
RXSPI
buffer. For larger
SPIBAUD
settings (
SPIBAUD > 4
),
RXS
is set before
SPIF
is set.
SPI Word Lengths
The processor’s SPI port can transmit and receive the word widths
described in the following sections.
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 ...