ADSP-2126x SHARC Processor Hardware Reference
9-43
Serial Ports
each SPORT. Companding is selected by the
DTYPE
field of the
SPCTLx
Control register.
Companding is supported on the A channel only. SPORTs 0, 2,
and 4 primary channels are capable of compression, while SPORTs
1, 3, and 5 primary channels are capable of expansion.
In Multichannel mode, when companding is enabled, the number
of channels must be programmed via the
NCH
bit in the
SPMCTLxy
register before writing to the transmit FIFO. The
MTxCSn
and
MTx-
CCsn
registers should also be written before writing to transmit
FIFO.
When companding is enabled, the data in the
RXSPxA
buffers is the
right-justified, sign-extended expanded value of the eight received LSBs. A
write to
TXSPxA
compresses the 32-bit value to eight LSBs (zero-filled to
the width of the transmit word) before it is transmitted. If the 32-bit value
is greater than the 13-bit A-law or 14-bit
-law maximum, it is automati-
cally compressed to the maximum value.
Since the values in the transmit and receive buffers are actually com-
panded in place, the companding hardware can be used without
transmitting (or receiving) any data, for example during testing or debug-
ging. This operation requires one cycle of overhead, as described below.
For companding to execute properly, program the SPORT registers prior
to loading data values into the SPORT buffers.
To compand data in place without transmitting:
1. Set the
SPTRAN
bit to 1 in the
SPCTLx
register. The
SPEN_A
and
SPEN_B
bits should be =0.
2. Enable companding in the
DTYPE
field of the
SPCTLx
Transmit
Control register.
3. Write a 32-bit data word to the transmit buffer. Companding is
calculated in this cycle.
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 ...