Coded data generation or conversion – Digital code to digital code converters – Coding by table look-up techniques
Patent
1997-10-20
1999-06-01
Williams, Howard L.
Coded data generation or conversion
Digital code to digital code converters
Coding by table look-up techniques
H03M 700
Patent
active
059091851
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a lookup table device and a signal conversion method. Particularly, it relates to a lookup table device for outputting an output signal previously defined in a table in response to a received input signal, and a signal conversion method used therein.
DESCRIPTION OF THE PRIOR ART
There is known a lookup table device for outputting a digital signal previously defined in a table, in response to a received digital input signal.
Such a lookup table device includes a memory having an n-bit address bus and a k-bit data bus, the address bus being used as an input signal line and the data bus being used as an output signal line. In the lookup table device, digital k-bit output signals are stored as a table in 2.sup.n storage areas which correspond to digital n-bit input signals, respectively. Thus, such a lookup table device requires a memory having a capacity of at least 2.sup.n .times.k bits.
Thus, this raised a problem in that if the value of n or k become larger, the table itself increased, resulting in increase of the necessary memory capacity. Particularly, if the value of n becomes larger, the necessary memory capacity exponentially increases in accordance with 2n. It was thus desired to provide a lookup table device which can reduce the memory capacity. If the necessary memory capacity increases in such a manner, time required to renew the table values will also increase. Therefore, this is not suitable for any application wherein the table values must be renewed at high speed.
In view of the aforementioned problem, an object of the present invention is to provide a lookup table device which can reduce the number of table values to be stored, resulting in reduction of the necessary memory capacity, and a signal conversion method used therein.
DISCLOSURE OF INVENTION
The present invention thus provides a lookup table device for converting a digital input signal into a digital output signal previously defined in correspondence to the digital input signal, comprising: representing a delimiter in the section of the digital input signal corresponding to the respective values of the digital output signal; signal belongs, based on the delimiter information stored in the delimiter information storage means, when the digital input signal is inputted; and to a section derived by the section deriving means.
According to the lookup table device of the present invention, each value of the digital output signals corresponds to any of the sections. In other words, the value of the digital input signal is divided into a plurality of sections. A digital input signal belonging to each section will correspond to a digital output signal having the same value.
When a digital input signal is inputted into the section deriving means, the section deriving means derives a section to which the digital input signal belongs on the basis of the delimiter information stored in the delimiter information storage means. The delimiter information stored in the delimiter information storage means is information required to derive the section to which the digital input signal belongs. Such information may be the value of the digital input signal representing the delimiter of the section, for example.
Thereafter, the signal output means outputs the digital output signal corresponding to the section derived by the section deriving means.
According to the present invention, it is not required to pre-store the same numbers of digital output signals which are equal value as all the successive values of the digital input signal, when the successive values of the digital input signals correspond to one and the same value of the digital output signals. This can reduce the necessary memory capacity.
As a result of reducing the number of table values which represent the relationship between the digital input and output signals, the table values can more quickly be written into the memory means.
In an aspect of the present invention, it is preferred that the signal output means includes output sign
REFERENCES:
patent: 5117385 (1992-05-01), Gee
patent: 5313611 (1994-05-01), Franklin et al.
Translation of JP 56-123037 A.
Miura Katsuhiro
Murata Hiroyuki
Yokota Takashi
Namco Ltd.
Williams Howard L.
LandOfFree
Lookup table device and signal conversion method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lookup table device and signal conversion method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lookup table device and signal conversion method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-957629