ADSP-2126x SHARC Processor Hardware Reference
9-7
Serial Ports
shows a block diagram of a serial port. Setting the
SPTRAN
bit
enables the data buffer path, which, once activated, responds by shifting
data in response to a frame sync at the rate of
SPORTx_CLK
. An application
program must use the correct serial port data buffers, according to the
value of
SPTRAN
bit. The
SPTRAN
bit enables either the transmit data buffers
for the transmission of A and B channel data, or it enables the receive data
buffers for the reception of A and B channel data. Inactive data buffers are
not used.
If the serial port is configured as a serial transmitter, the data transmitted
is written to the
TXSPxA/TXSPxB
buffer. The data is (optionally) com-
panded in hardware on the primary A channel (SPORT 0, 2, and 4 only),
then automatically transferred to the transmit shift register, because com-
panding is not supported on the secondary B channels. The data in the
shift register is then shifted out via the SPORT’s
SPORTx_DA
or
SPORTx_DB
signal, synchronous to the
SPORTx_CLK
clock. If framing signals are used,
the
SPORTx_FS
signal indicates the start of the serial word transmission.
The
SPORTx_DA
or
SPORTx_DB
signal is always driven if the serial port is
enabled (
SPEN_A
or
SPEN_B = 1
in the
SPCTLx
control register), unless it is
in multichannel mode and an inactive time slot occurs.
When the SPORT is configured as a transmitter (
SPTRAN = 1
), the
TXSPxA
and
TXSPxB
buffers, and the channel transmit shift registers respond to
SPORTx_CLK
and
SPORTx_FS
to transmit data. The receive
RXSPxA
and
RXSPxB
buffers, and the receive shift registers are inactive and do not
respond to
SPORTx_CLK
and
SPORTx_FS
signals. Since these registers are
inactive, reading from an empty buffer causes the core to hang
indefinitely.
If the SPORTs are configured as transmitters (
SPTRAN
bit = 1 in
SPCTL
), programs should not read from the inactive
RXSPxA
and
RXSPxB
buffers. This causes the core to hang indefinitely since the
receive buffer status is always empty.
If the serial data signal is configured as a serial receiver (
SPTRAN = 0
), the
receive portion of the SPORT shifts in data from the
SPORTx_DA
or
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 ...