JPS6089896A - Memory device - Google Patents

Abstract

PURPOSE:To decrease number of output terminals of a code name data by reading information to the outside of a chip while selecting sequentially each bit of information representing the memory code name. CONSTITUTION:Each digit of a code name means 10 consists of four columns and a code name of the decimal notation is obtained by using a binary hexadecimal notation to read binary information of each column. The output of each column is outputted sequentially via a selecting means 20. In this case, each column is selected sequentially by inputs I1-I4 and the binary information is transferred to the output gate via a transistor MT.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to read only memory (ROM) in integrated circuits, and to a ROM memory code name reading circuit.

In so-called mask convolution type ROM, which is a type of ROM whose memory contents are identified by a pattern in the manufacturing process, the memory code is permanently programmed during the manufacturing stage of the integrated circuit. Many 7'c products are produced, differing only in the memory code of the chip. These products are completely common except for their memory codes, and if they are mass-produced at the same time, L8I manufacturers often mix up lots.

Regarding lot contamination at the wafer stage, if the pattern remains on the phenol when the memory code is changed, it can be seen visually, and if the pattern does not remain (for example, due to ion implantation), it can be checked at the wafer stage. You can check the code with a simple probe check.

However, there is no way to confirm the code name in case of lot contamination after the chip is sealed in the case, and the current situation is to test with a test pattern that is deemed appropriate to prevent this kind of contamination accident. It is. If the test result is defective, the failure mode must be judged each time, whether it is due to a code error or a simple malfunction, and the lots must be separated, which takes a lot of time.

An object of the present invention is to provide a ROM code name reading circuit that allows the code name to be easily checked even after the chip is sealed, if it becomes necessary to read the code name of the ROM.

An example of a ROM code name reading circuit according to the present invention is shown in FIG. Figure 1 shows RO of 1000 bars from 000 to 999.
M code name? , is an example expressed in decimal notation. Each digit of the code name means IO consists of four columns. If the binary information in each column is expressed using the well-known binary coded hexadecimal system, it is expressed in decimal notation. It becomes the code name of the law. For example, each digit consists of four columns representing the numbers 8.4, 2.1, as shown in FIG. Column output is “1”
``It is possible to display hexadecimal numbers from θ to 15 by adding the numbers in each column of the level, but it is sufficient if decimal numbers from 0 to 9 are applied as code names.The output of each column is The transistors MLoad in the selection means 20 are Ml8 PI!iT for load resistance, and are sequentially outputted through the selection means.
Others are MI8 F for decoding to select 1 column out of 12 columns.
It is ET. Inputs 11-I select each column in turn and transfer the binary information to the output gate via MT.

, MT sets the read mode signal to L'' level and conducts when it becomes necessary to view the code name.

At this time, the output gate gives priority to code name reading, and the binary information of each column appears at the output terminal, so it is easy to change the gun using the binary coded hexadecimal system mentioned above. The input terminal and the gate controlling the selection means 20 can be completely shared with a normal logic operation path. Also, the output gate and output terminal O
UT can also be used in the same way. A dedicated test terminal may be used as the read mode signal terminal, or it may also be used as a normal input terminal if there is not enough terminal space. In that case, it is good to use ternary logic to distinguish between normal logical operations and the elucidation mode.

In this way, the ROM code name can be easily read without requiring any increase in the number of terminals or increasing the area.

The code name means of FIG. 1 consists of an announcement type and depression type M18 FET. This method is RO
This is a method applied when the M code is changed with the depletion shop MI8 PBT.The source and gate are at the ``0'' level of the substrate potential, so the depletion 7th gMI8
When the output of the FBT column becomes "0" level, the output of the enhancement MI8 FET column becomes "1" level.

In Figure 1, M,,, -,,Ml,,-4,M,,-,
,M,,-,.

, Ms-a, Ms-s*Ms-t are depressilon types,
Others are enhancement shops. The code name in this case is 398 based on comparison with the M2 diagram. The diagonally shaded F connected to the drain of each column is a metal flag arranged on the wafer so that the code name can be confirmed even when checking the probe.

Furthermore, the code name means is not limited to the example shown in Figure 1. For example, the code name means is enhancement shop MI8 F.
Made of BT, each source is commonly connected to the substrate potential, and each gate is commonly connected to the other 11L source potential.
” A means of determining.

Still another example is a MI8, in which each column is composed of a metal wiring, a polycrystalline silicon wiring III, a diffusion layer, and a wiring, without producing an FBT, and ul"l" depends on whether or not these wirings are connected to the substrate potential. There are means for determining 0''.

Further, the present invention can be applied to reading ROM codes in all manufacturing processes regardless of channel polarity, whether P channel, N channel, or complementary type.

In the present invention, the code name data is converted into bit serial data.
The code name data is output from the output terminal of the book, thereby reducing the number of output terminals for code name data. This means that when the output terminal is shared with a normal data output terminal, a terminal mode setting circuit is required as shown in the Ml diagram, but this mode setting circuit is 1g1N! This is because fewer is better in terms of scale. Therefore, in the present invention, a plurality of code name data are serially extracted one bit at a time while sequentially changing the data input from II to Step 4. In addition, especially its output circuit (column selection means)
20 is configured by forming a transfer gate gold tournament, so that bit serial data can be extracted with a very small number of parameters.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a ROM code name reading circuit of the present invention, in which a ROM code name displayed in three decimal digits is selected by an input signal and read out as binary information to one output terminal. This is an example. FIG. 2 is a diagram showing the well-known binary coded hexadecimal system. I, ~ Engineering 4... Input terminal, 10... Group...
...Code name means, 2o, target...column selection means. 1st item 2 Figure 2 difference 4ji / 631 wide

Claims (1)

[Claims] □ Provide an area in a part of a semiconductor chip having a memory circuit to store information indicating a memory code name consisting of a plurality of billets, and select each bit of the information indicating the memory code name sequentially while reading the chip from one output terminal. A memory device characterized in that the information is read out to the outside.