Recursive digital filter with reset

Details Recursive digital filter with reset Recursive digital filter with reset

1998-02-23

2000-12-26

Mai, Tan V.

Electrical computers: arithmetic processing and calculating

Electrical digital calculating computer

Particular function performed

708300, 708319, G06F 1710

Patent

active

06167415&

ABSTRACT:
An integrated circuit, e.g. an Audio Codec (AC) '97 conforming audio codec, includes a digital filter and gain module including multiple channels of gain control and multiple channels of digital filtering. A gain control module includes an overflow check of data samples requiring differing lengths of clamping. Each channel of the digital filter includes a finite impulse response (FIR) filter, and an infinite impulse response (IIR) filter. The digital filtering is implemented largely in hardware independent of the number of channels required and/or independent of the required order of the filtering. Thus, filter channels can be added or additional filtering implemented merely by increasing the clock speed without changing the digital filter design. The FIR filter is capable of being reset each frame to prevent a direct current (DC) buildup at internal nodes. The IIR filter performs a plurality of 2.sup.nd order biquadratic equations in an overall average of as few as four clock cycles per 2.sup.nd order biquad. A random access memory (RAM) is used to store the state variables for the 2.sup.nd order biquadratic equations. The state variable RAM is reset by controlling the clear input of latches at an input and/or the output of the state variable RAM, and the state variable RAM is addressed by a delta counter which is independent of the particular number of filter channels or filter orders implemented. Test patterns may be inserted between functional blocks of an integrated circuit such as the disclosed audio codec by appropriate control of the preset and clear inputs to output latches of the functional blocks.

REFERENCES:
patent: 4093850 (1978-06-01), Karnowski et al.
patent: 5418816 (1995-05-01), Yamamoto
Lee et al, "Digital Communication", Second Edition, .COPYRGT.1994 by Kluwer Academic Publishers, pp. 473-476.
Analog Devices et al., "Audio Codec '97; Component Specification; Revision 1.03; Sep. 15, 1996", Sep. 15, 1997.
Intel Corporation, "Audio Codec '97; Revision 2.0 Sep. 29, 1997", Sep. 29, 1997.

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