STA339BWS datasheet(59/79 Pages) STMICROELECTRONICS

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STA339BWS

7.7.6

Coefficient b0 data register bits (addr 0x23 - 0x25)

7.7.7

Coefficient read/write control register (addr 0x26)

7.7.8

Description

Coefficients for user-defined EQ, mixing, scaling, and bass management are handled

internally in the STA339BWS via RAM. Access to this RAM is available to the user via an

I2C register interface. A collection of I2C registers are dedicated to this function. One

contains a coefficient base address, five sets of three store the values of the 24-bit

coefficients to be written or that were read, and one contains bits used to control the

write/read of the coefficient(s) to/from RAM.

Three different RAM banks are embedded in STA339BWS. The three banks are managed

in paging mode using EQCFG register bits. They can be used to store different EQ settings.

For speaker frequency compensation, a sampling frequency independent EQ must be

implemented. Computing three different coefficients set for 32 kHz, 44.1kHz, 48 kHz and

downloading them into the three RAM banks, it is possible to select the suitable RAM block

depending from the incoming frequency with a simple I2C write operation on register 0x31.

For example, in case of different input sources (different sampling rates), the three different

sets of coefficients can be downloaded once at the start up, and during the normal play it is

possible to switch among the three RAM blocks allowing a faster operation, without any

additional download from the microcontroller.

To write the coefficients in a particular RAM bank, this bank must be selected first writing

bit 0 and bit 1 in register 0x31. Then the write procedure below can be used.

Note that as soon as a RAM bank is selected, the EQ settings are automatically switched to

the coefficients stored in the active RAM block.

Note:

The read write operation on RAM coefficients works only if RLCKI (pin29) is switching and

stable (ref. Table 8, tLRJT timing) and PLL must be locked (ref bit D7 reg 0x2D).

C5B23

C5B22

C5B21

C5B20

C5B19

C5B18

C5B17

C5B16

00000000

C5B15

C5B14

C5B13

C5B12

C5B11

C5B10

C5B9

C5B8

00000000

C5B7

C5B6

C5B5

C5B4

C5B3

C5B2

C5B1

C5B0

00000000

Reserved

000

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