AT76C002 Просмотр технического описания (PDF) - Atmel Corporation

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производитель

AT76C002

Programmable FIR Filter

Atmel Corporation 

Block Diagram

BXN

BXP

Backward Delay Line

FXP

Forward Delay Line

FXN

ALU

Coeffic-

ient

Bank

Register

Register

ALU

Coeffic-

ient

Bank

Register

Register

ALU

Coeffic-

ient

Bank

Register

Register

ALU

Coeffic-

ient

Bank

Register

Register

Adder Array

CLOCK

RESET

ADR

RD

DATA

WR/DS

CS

Control Unit

PRA

Configuration

Register

Output Gain

Register

Decimation

Control

Timing and

Control

Mux

Decimat-

ion

Dual-Port

RAM

Register

0 to

8-bit

Down

Shifter

8-bit

Down

Shifter

GAIN

DOUT

Internal Structure

FIR Structure

The AT76C002 is built around an array of 16 17x12 multi-

plier-accumulators, a forward and a backward delay line

which enable FIR filters of up to 32 taps to be implemented

with odd and even symmetry. FIR filters with interleaved

zeroed coefficients (such as half-band filters) are handled

in an efficient way since a 64 tap half-band symmetrical

FIR can be implemented in only one device.

Coefficient Banks

The AT76C002 contains 16 banks of 12 bit coefficients

that can be selected by writing to an internal register. The

12 bit coefficients are loaded using the 16 bit microproces-

sor data bus where the least significant 12 bits are for the

coefficient and the most significant 4 bits are for the ad-

dress within the bank. The bank number is selected by

writing to a configuration register.

Decimation

Using these coefficient banks, the AT76C002 can imple-

ment decimation filters by 2, 4, 8 or 16, the output rate

being 2, 4, 8 or 16 times lower than the input rate. The

value of the decimation is programmed in an internal con-

figuration register using the microprocessor interface. Us-

ing the SEN Sample Enable input signal, the circuit can

handle a variable incoming data rate.

Cascadability

The ATC76C002 can be cascaded in order to implement

long high-rate FIR filters. Even in a cascaded structure,

the AT76C002 can efficiently handle symmetrical and in-

terleaved zeroed coefficient FIR filters, by cascading both

forward and backward delay lines. In that way, a 128 tap

symmetrical FIR filter or a 256 tap symmetrical half-band

FIR filter would only require two cascaded AT76C002 de-

vices.

2

AT76C002

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