Pre-Processing Filter for Pre-Processing Filter for Audio ApplicationsAudio Applications

By Nathan Shaw, Lerzan By Nathan Shaw, Lerzan Celikkanat, and Xiangfeng WangCelikkanat, and Xiangfeng Wang

ELEC 422 VLSI Design 1 Fall 2005

OverviewOverview Implementing a low pass FIR filterImplementing a low pass FIR filter

4 taps4 taps 8-bit I/O, Two’s Complement8-bit I/O, Two’s Complement Major Components:Major Components:

FIFOFIFO 8-bit multiplier8-bit multiplier 16-bit adder16-bit adder PLA: control unit/ROMPLA: control unit/ROM

Filter Block DiagramFilter Block Diagram

ROMROM

6 words x 8-bits6 words x 8-bits Coefficient determined by Coefficient determined by

Control Unit by way ofControl Unit by way ofdecoder decoder

Control UnitControl Unit

INPUTS: Restart FailSafe NewInput;INPUTS: Restart FailSafe NewInput; OUTPUTS: S1 S2 S3 C0 C1 C2 Shift OUTPUTS: S1 S2 S3 C0 C1 C2 Shift

LoadI LoadC LoadMul LoadX LoadSum LoadI LoadC LoadMul LoadX LoadSum LoadFinal Clr1 Clr2LoadFinal Clr1 Clr2

WAITSelect coeff α3

GOTSIGNALLoad signal

S2=0

IDLEClear registers

Load RAM with zeros

SHIFT3 times

MULLoadI=1LoadC=1

ADDLoadMul=1LoadX=1SUM

LoadSum=1

STORELoadX=1Clr1=1

State MachineState Machine

Shift Select next coeff

X 4FINAL

LoadFinal=1

BYPASSS3=1

LoadI=1

(0,d)

(1,d)

(d,1)

16-bit Carry Ripple Adder16-bit Carry Ripple Adder

Composed of four 4-bit carry ripple addersComposed of four 4-bit carry ripple adders Two 16-bit inputs and one 16-bit outputTwo 16-bit inputs and one 16-bit output

MultiplierMultiplier

8 bit x 8 bit8 bit x 8 bit 16 bit output16 bit output

MultiplierMultiplier

FIFOFIFO

8 elements deep8 elements deep 8 bits wide8 bits wide

Output => αOutput => α33*x*x00 + α + α22*x*x11 + α + α11*x*x22 + α + α00*x*x33 + x + x44

xx44

xx33

xx22

xx11

xx00

xx00

XX44

XX33

XX22

xx11

xx44

xx33

xx22

xx11

xx00

xx11

xx00

xx44

xx33

xx22

xx44

xx33

xx22

xx11

xx00

xx33

xx22

xx11

xx00

xx44

xx44

xx33

xx22

xx11

xx00

xx22

xx11

xx00

xx44

xx33

shift1 shift2 shift6shift4 shift5

* α3

shift7shift3

* α2 * α1 * α0 * 1

OutputsOutputs

T0 => T0 => xx00 T1 => T1 => αα00*x*x00 + x+ x11 T2 => T2 => αα11*x*x00 + α+ α00*x*x11 + x+ x22

T3 => T3 => αα22*x*x00 + α+ α11*x*x11 + α+ α00*x*x2 2 + x+ x3 3

T3 => T3 => αα33*x*x00 + α+ α22*x*x11 + α+ α11*x*x2 2 + α+ α00*x*x3 3 + x+ x44

Tn => Tn => αα33*x*xn-3n-3 + α+ α22*x*xn-2n-2 + α+ α11*x*xn-1 n-1 + x+ xn n