Computer graphics processing and selective visual display system – Computer graphics display memory system – Addressing
Reexamination Certificate
1998-11-24
2001-07-17
Tung, Kee M. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics display memory system
Addressing
C348S714000, C348S718000
Reexamination Certificate
active
06262750
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on and claims the benefit of priority of the prior French Patent Application No. 9714727 filed on Nov. 24, 1997, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the storage of cues with different formats in a memory and to their reading therefrom.
The invention applies advantageously but not in a limiting fashion to the field of television, and more particularly to the storing of characters with different formats in and to their reading from a read-only memory intended to be read by the screen controller for the displaying thereon of the characters thus read.
2. Discussion of the Related Art
In graphics systems each character is generally represented over a certain number of bits, for example 9×13 corresponding to a matrix of 9×13 pixels. The format in which the characters are represented may be standardized, for example in the case of subtitling, or else can be free, especially as regards characters specifically dedicated to the television monitor.
An example is the so-called “menu” characters which allow symbols, such as a crossed-out loudspeaker, to appear on the screen to indicate that the sound from the television has been switched off. Moreover, whereas the characters with a 9×13 format are used, for example in the United States, certain countries which use a non-Latin alphabet require different character formats, for example an 18×26 format. Generally, one character format is required for a given application, for example a 9×13 format or an 18×26 format. At present, the design and construction of a system for storing and reading characters in a given format are specific to the format and such a system needs to be completely re-investigated, especially as regards the addressing of the memory for storing the characters, for a different character format. A solution for this problem is needed. An object of the invention is a device for storing and reading cues with different formats whose hardware and software architecture, especially as regards the addressing of the memory, is identical for these different formats of cues (e.g., a 9×13 format and an 18×26 format).
An object of the invention is also to achieve such a device in which the size of the storage memory is optimized and can be reduced or increased as a function of the number of characters to be stored whatever format is used, and without this requiring significant modifications to the structure of the addressing means.
Another object of the invention is to be able to store in the storage memory solely characters with a first format (for example 9×13) or else solely characters with a second format (for example 18×26) or alternatively characters with a first format and characters with a second format, and to do so while preserving the same addressing structure.
SUMMARY OF THE INVENTION
Briefly, in accordance with an aspect of the invention, in a process for storing cues with different formats in a memory, these cues, for example alphanumeric characters, comprise first cues with a first format (for example 9×13), each cue represented over a first number of bits (9×13) and each is identified by a first identifier coded over p+n+e bits (for example 11 bits), p (for example 8) and n (for example 2) being strictly positive integers and e (for example 1) being a positive or zero integer. The e bits (if any) are advantageously addressing expansion bits for flexibly increasing the number of characters which can be stored. The cues can also comprise second cues with a second format, each cue represented over a second number of bits greater than or equal to the product of the first number times 2
n
and each identified by a second identifier coded over p+e bits. In the case of a second format which is equal, for example, to 18×26, the second number of bits will be equal to the product of the first number (9×13) times 2
2
.
The memory comprises memory cells which can, depending on the structure of the memory, each contain 2
k
sets of bits, the number of bits of each set of bits being at least equal to the said first number (in this instance 9×13). Here, k is an integer greater than or equal to 0 and less than or equal to n and each memory cell can be designated by a cell address word of p+n−k+e bits.
Thus, according to a first characteristic of the invention, each second cue is split up, with a view to its storage, into 2
n
sets of bits shared out among one or more memory cells depending on the structure of the memory, that is to say depending on the value of k. If the second format under consideration is such that the second number of bits (for example 18×26) each representing a second cue is exactly equal to the product of the first number P
1
of bits (9×13) times 2
n
(in this instance 2
2
), then the number of bits of each set of bits which is contained in a memory cell is equal to the first number of bits (9×13). On the other hand, if the second format under consideration (for example 22×30) is such that the second number of bits lies between 2
n
.P
1
and 2
n+1
.P
1
(in this instance 2
2
.(9×13) <22×30<2
3
(9×13)), then the number of bits of each set of bits which is contained in a memory cell is greater than the first number of bits so as to allow the correct and complete representation of each second cue.
Furthermore, according to a process according to the invention, if k is zero, that is to say each memory cell (or memory word) contains just a single set of bits, each first cue is stored in the memory cell designated by a cell address word whose bits correspond to the p+n+e bits of the identifier of the first cue.
It should be noted here that within the meaning of the first invention, the verb “correspond” should be interpreted very broadly. More precisely, it is particularly advantageous in practice for the bits of the cell address word to be equal to the bits of the identifier of the first cue. This being so, provision could also be made for a predetermined table of correspondence between the value of the bits of the cell address word and the value of the bits of the identifier.
If k is non-zero, that is to say if each memory word or memory cell comprises several sets of bits, each first cue is then stored in a part of the memory cell designated by a cell address word whose bits correspond to the p+n+e−k high-order bits of the identifier of the first cue, this part of the memory cell thus designated being selected from among the 2
k
sets of bits contained in this designated memory cell, which selection is made with the aid of a selection word of k bits corresponding to the k low-order bits of the identifier of this first cue.
Furthermore, as regards the storage of a second cue (18×26 format, for example), if k is equal to n, this signifying that each memory cell or memory word contains 2
n
sets of bits, the 2
n
sets of bits forming each second cue are then stored in the memory cell designated by a cell address word whose e+p bits correspond to the e+p bits of the identifier of this second cue.
If k is different from n, this signifying that each second cue is then shared out among several memory cells, the two 2
n
sets of bits forming each second cue are stored in the 2
n−k
memory cells with consecutive addresses designated by 2
n−k
cell address words whose e+p high-order bits correspond to the e+p bits of the identifier of this second cue.
The storage process according to the invention therefore makes it possible to store the cues, whatever their format, in an optimized manner in the memory, that is to say without leaving “gaps” in the memory space used, that is to say without leaving a totally unoccupied memory cell between two occupied memory cells. Thus, stated otherwise, the invention allows storage of cues in me
Lusinchi Laurent
Tournier Christian
Bongini Stephen
Fleit, Kahn, Gibbons, Gutman & Bongini P.L.
Galanthay Theodore E.
STMicroelectronics S.A.
Tung Kee M.
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