Electrical computers: arithmetic processing and calculating – Electrical digital calculating computer – Particular function performed
Reexamination Certificate
1999-03-09
2001-10-23
Malzahn, David H. (Department: 2121)
Electrical computers: arithmetic processing and calculating
Electrical digital calculating computer
Particular function performed
Reexamination Certificate
active
06308191
ABSTRACT:
The present invention relates to a programmable co-processor circuit intended to be associated to a main processor for forming a digital filter, the circuit including at least a filter processor element having memory capacity for input data and for coefficients called “taps”, at least an adder and a multiplier of which one input is connected to a result output of the adder and another input is connected to a read output of the taps memory.
Such a circuit is notably used in applications where various filters are necessary, such as various multimedia applications, for example, for reducing intersymbol interference, for changing the data rate or for reducing the noise added by a communication channel.
A digital filter in essence includes a sequence of elements between which signals are tapped which are processed, notably multiplied by a tap and/or added together and are then re-injected elsewhere. For realizing digital filters, three paths are known:—utilization of a processor of the DSP type with specialized algorithms for forming a filter; if this path offers great flexibility, it has, however, limited filter performance, notably as regards speed,—utilization of specialized circuits directly forming filters; this permits great performance, but leads to a development of many different circuits,—utilization of specialized but programmable circuits; this provides a good compromise between the high performance of specialized circuits and the good flexibility of a DSP; among the programmable specialized circuits are distinguished processor programmable filters, which means that they are in essence formed by a DSP processor reduced to the minimum required by the process implemented in a filter. This is the most interesting solution.
A programmable specialized circuit includes memories for storing programmable taps. It is generally configured for realizing a particular type of filter: symmetrical, half-band, interpolation, decimation, adaptive, complex filter. An integrated circuit for a processor programmable filter is known from European patent application EP 0 454 050. The integrated circuit according to this document includes a multiplier and an adder, a memory for storing data and a program memory for storing sets of instruction codes and taps values, and a memory for instructions read from the program memory, which enables to execute an instruction while continuously reading the taps values. The integrated circuit includes a separate memory for the data and one for the taps, so as not to have to read the data at a time different from the time at which the taps are read.
It is an object of the invention to provide a programmable circuit that enables the multiplexing of different types of filters by utilizing the memory in optimum fashion, even when they have different requirements as regards memory size for storing the data and the taps.
For this purpose, the input data memory and the taps memory are placed in a single memory that is partitioned into various segments possessing a limited number of inputs/outputs, and means are provided for variably combining the segments in order to adapt the memory in optimum fashion to different filters.
The basic idea of the invention is thus to divide the memory between the data and the taps by using various memories, without increasing the size of the memory, which enables to use, for example, only an input port and two output ports, as is shown by an embodiment described below, so as to have the maximum efficiency at lower cost than that of a large memory with three input ports and five output ports. Actually, the surface of a memory much depends on the number of ports.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter, which constitute a non-limitative example.
REFERENCES:
patent: 5513223 (1996-04-01), Shoji
patent: 5793656 (1998-08-01), Richmond et al.
patent: 5904731 (1999-05-01), Matsui
patent: 6154761 (2000-11-01), Kondo et al.
patent: 6209013 (2001-03-01), Gonikberg
patent: 0454050 (1991-10-01), None
Dujardin Eric
Gay-Bellile Olivier
Malzahn David H.
U.S. Philips Corporation
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