AN3959 datasheet(45/65 Pages) STMICROELECTRONICS

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AN3959

Software setup to use the STA381BW/STA381BWS devices (ST Map)

Doc ID 022081 Rev 3

45/65

7.3

CRC computation

In the STA381BW/STA381BWS there are three different CRCs:

●

Biquad

●

Crossover

●

STCompressor

7.3.1

Biquad CRC computation

●

Download into RAM the biquad filter coefficients (address 0x00-0x27)

●

The XOR function calculates bit-to-bit the downloaded coefficients

●

Write the calculated coefficients in register BQCHKR (0x66-0x67-0x68)

●

Enable the BCGO bit (bit D0 register 0x6C). The checksum XOR of the biquad filter will

be exposed on the BQCHECKE registers (0x60-0x61-0x62)

●

Enable the CRC comparison, setting the BCCMP bit (bit D1 register 0x6C). The

comparison will be done on each audio frame and the result is written in BCCRES (bit

D2 register 0x6C)

–

BC_RES = 0 means that the checksum is OK, no errors

–

BC_RES = 1 means that checksum errors are detected

●

It is possible to reset the device if BC_RES = 1, enabling bit D3 of register 0x6C

(BCAUTO). By default, this function is disabled (BCAUTO=0)

7.3.2

Crossover CRC computation

●

Download into RAM the Xover filter coefficients (address 0x28-0x31)

●

The XOR function calculates bit-to-bit the downloaded coefficients

●

Write the calculated coefficients in register XCCKR (0x69-0x6A-0x6B)

●

Enable the XCGO bit (bit D4 register 0x6C). The checksum XOR of the Xover filter will

be exposed on the XCCKE registers (0x63-0x64-0x65)

●

Enable the CRC comparison, setting the XCCMP bit (bit D5 register 0x6C). The

comparison will be done on each audio frame and the result is written in XCRES (bit D6

–

XCRES=0 means that the checksum is OK, no errors

–

XCRES=1 means that checksum errors are detected

●

It is possible to reset the device if XCRES = 1, enabling bit D7 of register 0x6C

(XCAUTO). By default, this function is disabled (XCAUTO=0)

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