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ADSP-BF537 Blackfin Processor Hardware Reference
12-29
SPORT Controllers
These formats are applied to serial data words loaded into the
SPORTx_RX
and
SPORTx_TX
buffers.
SPORTx_TX
data words are not actually zero filled or
sign extended, because only the significant bits are transmitted.
Companding
Companding (a contraction of COMpressing and exPANDing) is the pro-
cess of logarithmically encoding and decoding data to minimize the
number of bits that must be sent. The SPORTs support the two most
widely used companding algorithms,
μ
-law and A-law. The processor
compands data according to the CCITT G.711 specification. The type of
companding can be selected independently for each SPORT.
When companding is enabled, valid data in the
SPORTx_RX
register is the
right-justified, expanded value of the eight LSBs received and sign
extended to 16 bits. A write to
SPORTx_TX
causes the 16-bit value to be
compressed to eight LSBs (sign extended to the width of the transmit
word) and written to the internal transmit register. Although the com-
panding standards support only 13-bit (A-law) or 14-bit (
μ
-law)
maximum word lengths, up to 16-bit word lengths can be used. If the
magnitude of the word value is greater than the maximum allowed, the
value is automatically compressed to the maximum positive or negative
value.
Lengths greater than 16 bits are not supported for companding operation.
Table 12-4. TDTYPE, RDTYPE, and Data Formatting
TDTYPE or
RDTYPE
SPORTx_TCR1 Data Formatting
SPORTx_RCR1 Data Formatting
00
Normal operation
Zero fill
01
Reserved
Sign extend
10
Compand using
μ
-law
Compand using
μ
-law
11
Compand using A-law
Compand using A-law
Содержание Blackfin ADSP-BF537
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Страница 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
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Страница 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Страница 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...