JPS589292A - Reading system for read only memory device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the method of squeezing out the continuous storage device 1 (hereinafter referred to as ROM). The output value is determined by logic processing and the defects of each ROM are corrected.
Regarding OM and the RAM extraction method. In order to memorize the kanji 0, which has recently become more and more often used in computer output, it requires a large number of memory cells to memorize the 0 kanji character, as it has a larger number of characters than the alphabet or kana. For this reason, ROMs that store a large number of kanji characters have a large capacity and are so large that, for example, only one ROM can be manufactured from a wafer. For this reason, the yield is low, and in the past, the output was determined by using two defective ROMs and calculating the logic of their outputs, and the complementary effect was used to create one complete ROM to improve the yield.

FIG. 1 is a diagram showing the principle of construction of a kanji ROM circuit, and is a diagram in which mountains are output. FIG. 2 is a diagram showing an error caused by a cell defect, and FIG. 3 is a block diagram when correction is performed using two defective WIlbROMs in the conventional example.

1 in the figure. ．． 21,3 is ROM14 is or (ro) road, λ1
~A1・ is the dot position address within the character, AI, ~A1
1 is a letter-specific address, 11 of 0 in Figure 1! is white, 'O'
indicates black. Now, give 1%-AM to the ROM1 of the prisoner in Figure 1, 1%-AM, and give the addresses 1 to 1 of the dots within the characters. When , data necessary for the corresponding character is read out as shown by @0. In FIG. 1@0, a character is represented by 10xlO-100 91 # % Q #, making one character with a total of 100 addresses. However, if there is a defect in a certain position of a ROMI cell, correct output cannot be obtained. For this reason, defective ROMs were made unreliable. This yield improvement measure will be observed below. 2nd WA (
s) The point should be 10” (black) but is now 11’ (white)←
) points indicate the case where an error occurs in the opposite case.In this case, if the (b) path as shown in FIG.
As shown in Cf), there is a defect in one of the ROM cells.
Even if Q becomes l, if the other ROM is 11#, the output will be %
1', so the defect shown in -) disappears. But 0)
Such defects will not go away. However, the actual large capacity fiRO
Since M can be devised in the circuit so that defective cells tend to output either 10' or 11', if M tends to output 10' according to this tendency, the OR circuit 4 is used as shown in Figure 3. If the result is likely to be 111, an AND circuit is used. By doing so, it is possible to correct the defective ROM by using two defective ROMs and improve the yield to some extent. However, in this method, whether to use an OR circuit or an AND circuit depends on the ROM, so if an OR circuit is used, the defects as shown in Figure 2 (c) cannot be removed, and if an AND circuit is used, the second Defects such as those shown in Figure (b) cannot be removed, and in this case, the ROM has no choice but to be considered defective, and has the disadvantage that it is not possible to improve the processing speed beyond a certain degree.

The purpose of the present invention is to eliminate the above-mentioned drawbacks by using three or more defective ROMs to almost completely correct the defective cells in the ROM and to provide a high-yield ROM that can be used as one complete ROM. [Providing a delivery method]

In order to achieve the above object, the present invention provides three or more successive storage devices of the same type storing data of the same content.
Give the same read cell designation address, compare the output information from each successive read-only storage device, and if there is a difference, create a criterion for selecting one or the other, determine the output value, and transfer that value to the read-only storage device. This is a read-only storage device read method characterized by using read information.

An embodiment of the present invention will be described below with reference to the drawings. Fourth
The figure is a block diagram when correction is performed using three defective ROMs according to an embodiment of the present invention.

Items with the same functions as those in Figure 1 are indicated by the same symbols, s, 2g.
, 7 is a ROM, and 8 is a majority circuit.

)t+OMs, , 6e, and 7 are the same type of ROMs that store the same data and have the same address content.

Therefore, ROM5. ．． All character-specific addresses in 61 and 7
Given S-AM, the address of the dot in the character A, ~A,.

When , the output JI or 11' having the same content is output, and the majority decision is taken by the majority circuit 8, and the result is output as the output of one ROM. Even if there is a defect as shown in FIG. Therefore, in this case, two ROs
If M does not have a defective cell at the same location, either type of defect can be removed (see Figure 2). Therefore, in this case, there is no need to create a circuit in which the defective cells are easily fixed using 10#, and since two ROMs rarely have defective cells in the same position, the defective ROM is By using two complete ROMs, the production yield can be improved. This embodiment was explained by using 3s of defective ROMs, but the number of defective ROMs may be four or more, and the majority circuit uses, for example, four defective ROMs to correct for a difference of one or less. You may use a method of judgment that takes this into account.

As described in detail above, according to the present invention, three or more defective ROMs can be used as one complete R, OM, thereby improving the yield of large capacity ROMs.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration principle of the Kanji ROM circuit, which outputs mountains, Figure 2 is a diagram showing errors due to cell defects, and Figure 3 is correction using two defective ROMs in the conventional example. Figure 4 is a block diagram of the case where correction is performed using three missing ROMs according to the embodiment of the present invention. 1 and 2 in the diagram
□3. ．． 5h, 6. , '1 is the ROM, 4 is the OR circuit, 8 is the majority circuit, Bird~Al11 is the dot position address within the character, A□~Ax is the address for each character, 1 in Figure 1 0
1# indicates white and '0# indicates black. Agent 1 - Physician Matsu - Hiroshi-Nyun Figure 1 (Bn11//lθ//ll 1llllθ///1 1111/lllllI

Claims (1)

[Claims] 3 or more *a of the same noodles that memorized the same self-answer data
+ Dedicated memory device, same - Give the designated address of the translation cell, compare the output information from each translation dedicated memory device, and if there is a difference, create a judgment criterion to select one or the other, and determine the output value. and the value thereof is used as read information of the successive-only storage device iIL.