Datasheet

STA309A Registers
Doc ID 13855 Rev 4 59/67
7.6 Writing a set of coefficients to RAM
1. write top 2-bits of starting address to I
2
C register 0x3B
2. write bottom 8-bits of starting address to I
2
C register 0x3C
3. write top 8-bits of coefficient b1 in I
2
C address 0x3D
4. write middle 8-bits of coefficient b1 in I
2
C address 0x3E
5. write bottom 8-bits of coefficient b1 in I
2
C address 0x3F
6. write top 8-bits of coefficient b2 in I
2
C address 0x40
7. write middle 8-bits of coefficient b2 in I
2
C address 0x41
8. write bottom 8-bits of coefficient b2 in I
2
C address 0x42
9. write top 8-bits of coefficient a1 in I
2
C address 0x43
10. write middle 8-bits of coefficient a1 in I
2
C address 0x44
11. write bottom 8-bits of coefficient a1 in I
2
C address 0x45
12. write top 8-bits of coefficient a2 in I
2
C address 0x46
13. write middle 8-bits of coefficient a2 in I
2
C address 0x47
14. write bottom 8-bits of coefficient a2 in I
2
C address 0x48
15. write top 8-bits of coefficient b0 in I
2
C address 0x49
16. write middle 8-bits of coefficient b0 in I
2
C address 0x4A
17. write bottom 8-bits of coefficient b0 in I
2
C address 0x4B
18. write 1 to WA bit in I
2
C address 0x4C
The mechanism for writing a set of coefficients to RAM provides a method of updating the
five coefficients corresponding to a given biquad (filter) simultaneously to avoid possible
unpleasant acoustic side-effects.
When using this technique, the 10-bit address would specify the address of the biquad b1
coefficient (for example, decimals 0, 5, 10, 15, …, 100, … 395), and the STA309A will
generate the RAM addresses as offsets from this base value to write the complete set of
coefficient data.