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.
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 ...