TAS3202 datasheet(34/69 Pages) TI2

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40 39

32 31

24 23 22 21 20 19

16 15

8 7

16-Bit Audio

18-Bit Audio

20-Bit Audio

24-Bit Audio

Precision/Noise Bits

Overhead/

Guard Bits

(-73)

(-51)

(-124)

(-45)

(57)

(59)

(-110)

-73

-124

-110

-51

-45

Rollover

TAS3202

SLES208B – JUNE 2009 – REVISED MARCH 2011

www.ti.com

7.1

DAP Instructions Set

Please see this information in the TAS3xxx DAS Instruction Set Reference Guide, available to those

registered to the TAS3xxx-PurePath Studio Extranet.

7.2

DAP Data Word Structure

Figure 7-2 shows the data word structure of the DAP arithmetic unit. Eight bits of overhead or guard bits

are provided at the upper end of the 48-bit DAP word, and 16 bits of computational precision or noise bits

are provided at the lower end of the 48-bit word. The incoming digital audio words are all positioned with

the MSB abutting the 8-bit overhead/guard boundary. The sign bit in bit 39 indicates that all incoming

audio samples are treated as signed data samples The arithmetic engine is a 48-bit (25.23 format)

processor consisting of a general-purpose 76-bit ALU and function-specific arithmetic blocks. Multiply

operations (excluding the function-specific arithmetic blocks) always involve 48-bit DAP words and 28-bit

coefficients (usually I2C programmable coefficients). If a group of products is to be added together, the

76-bit product of each multiplication is applied to a 76-bit adder, where a DSP-like multiply-accumulate

(MAC) operation takes place. Biquad filter computations use the MAC operation to maintain precision in

the intermediate computational stages.

Figure 7-2. Arithmetic Unit Data Word Structure

To maximize the linear range of the 76-bit ALU, saturation logic is not used. In MAC computations,

intermediate overflows are permitted, and it is assumed that subsequent terms in the computation flow

correct the overflow condition (see Figure 7-3). The DAP memory banks include a dual port data RAM for

storing intermediate results, a coefficient RAM, and a fixed program ROM. Only the coefficient RAM,

accessible via the I2C bus, is available to the user.

Figure 7-3. DSP ALU Operation With Intermediate Overflow

Digital Audio Processor (DAP) Arithmetic Unit

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