Companding - Analog Devices Blackfin ADSP-BF537 Hardware Reference Manual

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Table of Contents

Table 12-4. TDTYPE, RDTYPE, and Data Formatting

These formats are applied to serial data words loaded into the

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

right-justified, expanded value of the eight LSBs received and sign

extended to 16 bits. A write to

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

Lengths greater than 16 bits are not supported for companding operation.

ADSP-BF537 Blackfin Processor Hardware Reference

SPORTx_TCR1 Data Formatting

Normal operation

Compand using μ-law

Compand using A-law

SPORTx_RCR1 Data Formatting

Compand using μ-law

Compand using A-law

data words are not actually zero filled or

causes the 16-bit value to be

SPORT Controllers