Electrical computers: arithmetic processing and calculating – Electrical digital calculating computer – Particular function performed
Reissue Patent
1997-10-08
2001-02-06
Moise, Emmanuel L. (Department: 2784)
Electrical computers: arithmetic processing and calculating
Electrical digital calculating computer
Particular function performed
C708S232000, C326S040000, C326S041000
Reissue Patent
active
RE037048
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to integrated circuits and, more specifically, to user-programmable integrated circuits. More particularly, the present invention relates to user-programmable mixed analog and digital integrated circuits.
2. The Prior Art
General purpose linear integrated circuits have limited themselves to specific functions such as operational amplifiers, phase locked loops, comparators, A/D converters, video amplifiers, transistor arrays, etc. These circuits form the building blocks of analog systems. Integrating these circuits into higher functions is difficult due to the need to employ external components (i.e., resistors, capacitors, inductors, etc.) to determine their exact function. Thus once integrated, these circuits become specialized. In order to be practicable for design, manufacture, and sale, such a specialized part must have a large usage base. One illustrative example of such a circuit is an audio amplifier which may be used in stereo systems or television sets. Without a large usage base, the design and manufacture of such a circuit is not economical.
During the manufacture of analog circuits a significant cost is the final trimming of each individual circuit. This is required because
actual
component values vary as well as stray capacitance
is introduced
due to component placement.
Another common problem in electronics is that various parts of a complex signal need to be kept in phase while utilizing different circuit paths.
This
For example, this
is commonly done in color television sets where the luminance information is routed through a delay line while the chrominance information is processed.
Furthermore, many common analog systems such as television sets,
VCR's
VCRs
and stereo systems are currently employing many digital functions. Hence the integration of these circuits onto a single integrated circuit die requires mixed analog and digital design and a process to manufacture
them
such integrated circuits
. The manufacturing process for such integrated circuits is complex and expensive as the transistors used in analog circuit design are typically radically different from those used in digital design.
One
prior-art
prior art
approach to this problem has been to design circuits which operate employing digital signal processing (DSP) techniques.
These devices use
Such circuits employ
a microprocessor core to simulate the mathematical equivalent of the analog system. One common application for such
chips
circuits
is digital filtering of
the
digitized analog
signals before conversion
of such signals
back to
the
analog
world
.
A fundamental limitation of
these
integrated DSP devices is that the device speed is limited by the Von Neuman architecture of the microprocessor where many processor functions are required for each time slice of the analog signal. This limitation has heretofore limited the speed of such devices to frequencies in the audio spectrum. This is of course due to the fact that the customization of the function is achieved by the coding of the instructions in the microprocessor.
Another approach to the mixed analog and digital integrated circuit is shown in U.S. Pat. No. 5,107,146 to El-Ayat. This patent discloses a user-programmable architecture including a mixture of analog and digital circuit modules. The digital logic modules are of the type used in prior field programmable gate array (FPGA) devices.
Work has been done in the past in trying to design processor arrays to speed up applications.
These
This
class of machines
are
is
called MIMD or SIMD (multiple instruction multiple data or single instruction multiple data). These concepts utilize a plurality of processor engines to perform logical operations, such as multiplication and division. Each processor engine is a Von Neuman machine and occupies significant die area on an integrated circuit.
It is an object of the present invention to provide a user-programmable digital signal processing integrated circuit which overcomes the limitations of the prior art.
It is another object of the present invention to provide a user-programmable digital signal processing integrated circuit which does not require individual
component
trimming to maximize performance.
Yet another object of the present invention is to provide a user-programmable digital signal processing integrated circuit which allows the user to control phase shifting of signals being processed therein.
It is a further object of the present invention to provide a user-programmable digital signal processing integrated circuit which may be easily programmed by a user.
BRIEF DESCRIPTION OF THE INVENTION
According to the present invention, a field programmable, digital signal processing integrated circuit is formed in a semiconductor die and includes an array of arithmetic logic unit (ALU) circuits. A user programmable interconnect architecture is superimposed on the array of ALU circuits. One or more interface circuits comprising digital-to-analog (D/A) converters or analog-to-digital (A/D) converters are provided on (or off) the integrated circuit to interface to off-chip analog input signals and provide off-chip analog output signals. Other functional circuit blocks, such as programmable read only memory (PROM) or Random Access Memory (RAM) circuits may also be disposed on the integrated circuit die. Circuitry is provided to program the interconnections between the interface circuits and the ALU circuits and between individual ones of the ALU circuits, as well as to define the specific functions of the individual ALU circuits.
The architecture of the present invention avoids the Von Neuman bottle neck characteristic of prior art systems by eliminating the need for sequential instructions. Each ALU circuit of the present invention may be user customized to act like the mathematical equivalent of an analog circuit element. The individual ALU circuits are interconnected to one another and to A/D and D/A interface circuits by user-programmable interconnect elements.
REFERENCES:
patent: 4870302 (1989-09-01), Freeman
patent: 5107146 (1992-04-01), El-Ayat
patent: 5200751 (1993-04-01), Smith
patent: 5231588 (1993-07-01), Agrawal et al.
Actel Corporation
Moise Emmanuel L.
Schafer Jonathan H.
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