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.
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 ...