Computer graphics processing and selective visual display system – Display driving control circuitry
Reexamination Certificate
1999-10-26
2002-02-19
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Display driving control circuitry
C345S087000, C345S096000, C345S098000
Reexamination Certificate
active
06348915
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the process of transferring data in parallel with a plurality of data lines utilized in the interior of a computer or its associated equipment. More particularly, the invention relates to inverting data in accordance with an efficient majority decision in order to reduce the number of data-bit changes (the number of data transitions) in the case transferring signals in parallel through a plurality of data lines (buses, etc.).
2. Description of the Related Art
In the interior of a computer or its associated equipment, data transfer is performed in an extremely wide range and generally data signals are transferred and processed in parallel through a great number of data lines from the necessity of processing data in large quantities and at high speed. More specifically, when n data bits (where n is a natural number) are transferred, n data lines are prepared and n (n-system) data bits changing in a time series manner are transferred in parallel from a transmitter to a receiver through the n data lines.
The data bits changing in a time series manner make a transition between a logic 0 and a logic 1. Note that the discrimination between a logic 0 and a logic 1 is performing by treating a voltage less than a predetermined voltage as a logic 0 and a voltage greater than the predetermined voltage as a logic 1.
A set of data lines, which are prepared for transferring a plurality of data bits thus changing in a time series manner, form a data-transferring width in data transfer and is generally called a bus. The bus, as hardware, includes all signal-transferring media and wires that can transfer signals in a broad sense. In a narrow sense, the bus, as a set of wires, can also be grasped as a separable component (there are cases where it includes a connector, etc.) called an interface cable or the like.
It is well known that unnecessary radiation of electro-magnetic waves will arise when data is transferred. Therefore, attention has been paid to a possibility that unnecessary radiation will be an obstacle to other constituent elements in the interior of electronic equipment and an obstacle to peripheral electronic equipment. As a basic countermeasure on a hardware side for preventing unnecessary radiation such as this, there is an elaborate measure of individually setting a filter to each data line.
A measure such as this is collectively called an electro-magnetic interference (EMI) countermeasure and is a countermeasure to pass an allowable value (standard value) determined in specific groups and countries or in the world as a product or an entire system.
The reason why a measure is thus aimed primarily at data lines is that it is seen that EMI radiation often becomes a problem in the case where it arises from a bus or an interface cable serving as a set of data lines than in the case where it arises from internal circuitry. The reason, as also described later, is that an interface cable has a property that it serves as an antenna for EMI radiation and increases EMI radiation, as it becomes longer. In most cases, an interface cable or the like is a separable component for connecting apparatuses separated from each other, so the cable requires a certain degree of length so that it can be widely used.
Presently, the high-density of the hardware in a computer and its associated equipment has advanced, so the complexity is rapidly increasing. An increase in the number of data lines is closely related to this EMI radiation. Particularly, in liquid crystal displays (LCDs), a great number of pixels are disposed for the high density in a display, and in order to these pixels individually, a great number of data lines, such as source lines, gate lines and the like, are provided. Therefore, a total of data lines for realizing data transfer becomes extremely enormous.
FIG. 1
illustrates the constitution of an LCD module
10
employing thin film transistors (TFTs) as an example of an LCD. The digital data bus-clock
20
extending from a gate array
11
is elaborately connected to an X-driver (also called a data driver or a source driver)
30
and a Y-driver (also called a gate driver)
40
, whereby a TFT on a pixel electrode specified by X and Y can be driven.
The gate array
11
in this example is also called an LCD controller
11
by the fact that it controls the supply of signals to these drivers. The LCD controller and the drivers, as hardware, are realized as internal logic devices internally wired, such as LSI circuits. In color LCDs, pixel electrodes are alternately required individually every three colors: red, green, and blue. For this reason, the number of data lines becomes extremely enormous.
In the case of an LCD module as hardware, there are cases where it includes not only a panel (in which a liquid crystal is interposed between two glass substrates) but also peripheral members such as a back light. Furthermore, there are cases where it includes up to connector terminals that are connected to a system. Therefore, the meaning of the term “LCD module” is not to be limited to the constitution expressed in
FIG. 1
but should be interpreted widely.
Incidentally, it is known that there are the following relations (a)-(c) (general properties) between data transfer and EMI radiation.
(a) When digital signals of the same waveform are sent on n interface cables, the EMI radiation becomes n times the case where the digital signal is sent on a single interface cable.
(b) EMI radiation is proportional to the frequency component of a signal and becomes stronger as the repetition of a signal becomes faster. For instance, in the case where a digital signal simply repeats a logic high, a logic low, (1010 as pulse display, H is high, L is low) a logic high, and a logic low, the strongest EMI radiation arises. This is because a change in data bits per unit time (in this example, 4 bits), which is sent in a time series manner, will arise most frequently.
(c) An interface cable serves as an antenna for EMI radiation and therefore increases EMI radiation, as the cable becomes longer. That is, an external portion extending as a cable and the length thereof become a problem.
With these relations (general properties) as a premise, a contrivance for reducing EMI radiation, particularly based on the relation of (b) (general property), can be divided into the following (A)-(G).
(A) Reduce the number of data-bit changes themselves during data transfer.
(B) Invert (or process) all or some of data bits in order to reduce the number of data-bit changes.
(C) Contrive a method of evaluating the number of data-bit changes.
(D) Simplify a method of evaluating the number of data-bit changes.
(E) Reduce unnecessary radiation by a reduction in the number of data-bit changes.
(F) Reduce power dissipation by a reduction in the number of the data-bit changes.
(G) Select a method of utilizing the evaluation result of the number of data-bit changes.
These contrivances of (A)-(G) will be examined one by one.
First, as a conventional technique regarding (A), there is Published Unexamined Patent Application No. 8-79312. This technique processes data bits in a time series manner with respect to specific data bits (in which 1, 0, 1, and 0 are alternately transferred) that are considered as the worst case that will cause unnecessary radiation, thereby reducing the number of data-bit changes. This technique exhibits effect under a specific condition without particularly adding a redundant inverting signal. However, there are cases where the result of data processing will have an adverse effect on a reduction in the number of data-bit changes. Although it is described that the case having an adverse effect can be avoided by addition of a redundant inverting signal, there is no description of how the case having an adverse effect is avoided by addition of a redundant inverting signal.
Here, a conventional technique regarding (B) inverts data bits so that the number of data-bit changes is minimized, and transfers the inverted data bits a
Nakano Masashi
Yamashita Hiroshi
Dinh Duc Q.
Hjerpe Richard
Underweiser Marian
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