JP3462956B2 - Mask ROM data generator - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a mask ROM (Mas ROM).
The present invention relates to a mask ROM data generator that generates a netlist, a layout pattern, data indicating a logical simulation model, and the like, which are necessary in the development and manufacturing of a k read only memory) based on a ROM code, a bit width, and the number of words.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor integrated circuits,
The scale of mask ROM is increasing, and a megabit class mask ROM is being used as an ASIC (Application Specific
It is becoming possible to incorporate it into a grated Circuit) (IC for a specific application).

In a mask ROM which is a read-only semiconductor memory device, information is written at the manufacturing stage by using a mask corresponding to a ROM code provided by a customer. The layout pattern, the netlist, the test pattern, the data showing the logical simulation model, etc. necessary for the development / manufacturing of the mask ROM are stored in the mask ROM.
It is generated by the data generator based on the ROM code and the preset bit width and number of words. Mask ROM
The amount of these data generated by the mask ROM data generator is also increasing with the increase in the scale of the above, and especially the amount of data of the layout pattern and the netlist is remarkably increased.

The netlist generated by the mask ROM data generator is for verifying whether or not the circuit configuration realized by the layout pattern is the same as the circuit configuration shown by the netlist. Since the layout pattern of the mask ROM itself and the netlist are generated by the same mask ROM data generator based on the same input data, there is no need for verification. Therefore, in this case, it is not necessary to generate a netlist. However, if the mask ROM is
When incorporated as a part of the SIC chip, a netlist is required to detect an error such that a layout pattern other than the mask ROM overlaps the layout pattern area of the mask ROM.

[0005]

Conventionally, a netlist has been generated in units of a transistor level circuit corresponding to each bit forming a ROM code. Therefore, when the scale (storage capacity) of the mask ROM increases,
The amount of data in the netlist also increased in proportion to its scale. On the other hand, in the mask ROM of the method of reflecting the ROM code by metal wiring or the like, for example, circuits for 8 bits are collectively made into one block, and this block is commonly used to put the ROM code in a wiring form outside the block. By the method of reflecting, the netlist can be described hierarchically to reduce the data amount.

However, in a mask ROM (hereinafter referred to as a "depletion type ROM") constructed by using depletion type transistors, the transistor level circuit configuration corresponding to each bit of the ROM code changes depending on the content of the ROM code. Therefore, in such a case, unlike the above-mentioned mask ROM in which the ROM code is reflected by metal wiring or the like, the circuit configuration cannot be described hierarchically.

In view of this, the present invention provides a mask ROM data generator capable of reducing the data amount of a netlist by describing the circuit structure of the depletion type mask ROM in a hierarchical manner. To aim.

[0008]

SUMMARY OF THE INVENTION A mask ROM data generator according to the present invention made to solve the above problems inputs a ROM code, a bit width and the number of words of a mask ROM and outputs the mask ROM data. In a mask ROM data generator having a function of generating a netlist describing a circuit configuration, a blocking means for collecting the ROM code into a plurality of bits to form blocked data,
For each type of blocked data obtained by the blocking means, the mask R corresponding to the blocked data
A local netlist creating means for creating a local netlist describing the circuit configuration of the OM, and a hierarchical circuit configuration of the mask ROM using the circuits corresponding to the respective blocked data as constituent elements while referring to the local netlist. And an entire-area netlist creating means for creating the entire-area netlist described in 1.

In the mask ROM data generating device, the blocking means sets the number of bits of the blocked data to an integer which is a divisor of the number of words smaller than the number of words and which is equal to or less than a preset value. Of these, the maximum value is preferable.

[0010]

According to the mask ROM data generator of the present invention, since the netlist hierarchically describing the circuit configuration of the mask ROM is generated, the data amount of the netlist can be reduced. When the amount of data in the netlist is reduced, the time required to generate the netlist is also reduced. Further, compared to a device that outputs a circuit diagram, the mask ROM data generator of the present invention needs to convert the circuit diagram into a netlist when checking whether the circuit realized by the layout pattern has a predetermined configuration. It is advantageous in that it does not exist.

According to the preferred mask ROM data generator of the present invention, the number of bits of the blocked data is a divisor of the number of words smaller than the number of words and is an integer less than or equal to a preset value. Since it becomes the maximum value, a relatively large size of blocked data can be obtained within a range in which the probability that the types (values) of a plurality of blocked data are the same does not decrease significantly. Therefore, the hierarchical description makes it possible to greatly reduce the data amount of the netlist.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION <Overall Configuration of Embodiment> FIG. 1 is a block diagram showing a hardware configuration of a mask ROM data generator according to an embodiment of the present invention.
As shown in this figure, the mask ROM data generator is
The processing device 10 includes a hard disk device 12 as an external storage device, a keyboard 14 and a mouse 15 as input devices, and a display device 20. The processing device 10 includes a CPU (central processing unit) 16 and a memory 18 as a main memory, and the CPU 16 executes a predetermined program stored in the memory 18 to function as a mask ROM data generation device. Is realized. That is, when the operator activates a predetermined program and inputs parameters for defining the mask ROM configuration such as the bit width and the number of words from the keyboard 14 and the mouse 15, the ROM code previously stored in the hard disk device is read into the memory 18. , These parameters and RO
Based on the M code, a function of generating a layout pattern, a netlist, a test pattern, data indicating a logical simulation model, and the like, which are necessary in the development and manufacturing of the mask ROM, is realized.

<Operation of Embodiment> Next, of the operation of the mask ROM data generator having the above-described structure, a portion related to the present invention, that is, a portion for generating a netlist will be described. The processing executed to generate the netlist is realized by a netlist generation program which is a part of a predetermined program stored in the memory 18. The operation of netlist generation will be described below with reference to FIG. 3 showing an example of a circuit corresponding to a ROM code (hereinafter referred to as “ROM code circuit”).

FIG. 3 is a diagram showing an example of a ROM code circuit in the depletion type mask ROM. In this example, the ROM is composed of 8 words, one word is composed of 4 bits, and the ROM code circuit has two types of depletion type MO corresponding to data "0" and "1".
It is realized using an S transistor. The word lines W0 to W7 are connected to the gates of the transistors corresponding to the bits forming each word, and the first bit (least significant bit) to the fourth bit (most significant bit) of the eight words are connected. Eight transistors corresponding to each bit are connected in series with two selection transistors connected in series in the center. The series-connected circuits corresponding to the bits forming the word are grounded at both ends, and the bit lines B0 to B3 are connected to the connection points of the two central selection transistors.

FIG. 2 is a flowchart showing a part of the operation of the mask ROM data generator of this embodiment for generating a netlist. When the netlist is generated by the mask ROM data generator of the present embodiment, first, in step S10, parameters that define the structure of the mask ROM, that is, auxiliary parameters such as the bit width, the number of words, and the buffer size are set. The operator makes settings using the keyboard 14 and the mouse 15. For example, in the case of the example shown in FIG. 3, the bit width is 4 and the word number is 8
And a parameter indicating that it is a NAND type configuration using a depletion type transistor.

Next, in step S12, the ROM code stored in advance in the hard disk device 12 is read into the memory 18, which is the main memory.

Thereafter, in step S14, the bits per block when the ROM code is collectively grouped into a plurality of bits in the subsequent step based on the ROM configuration determined by the set parameters and the read ROM code Determine the number (hereinafter referred to as "block size"). Here, the block size is selected to be the maximum value of integers that are a divisor of the number of words smaller than the number of words and are in the range of about 2 to 16. For example, if the number of words is 1024, the divisor is 2, 4,
Since it is 8 and 16, the maximum value of these is 16
Is selected as the block size. In this case, there are 65536 bit patterns of blocked data.
The reason why the selection range is limited to 2 to 16 is that if the block size becomes too large, the number of types of bit patterns that can be taken by the blocked data becomes too large, and blocked data having the same bit pattern can exist. This is because the sex is reduced. In other words, if there is a small amount of blocked data having the same bit pattern, the netlist data amount may not be reduced even if a circuit is hierarchically described based on this blocking in a step described later. In the case of the example shown in FIG. 3, the number of words is 8
Therefore, 4 is selected as the block size.

When the block size is selected as described above, the ROM code is grouped into blocks for each block size, and a netlist in which the circuit configuration is hierarchically described is generated based on the block. For this purpose, first, in step S16, the ROM codes corresponding to any one bit line in the ROM code circuit are grouped into blocks for each block size. As a result, a plurality of pieces of blocked data having the number of bits of the block size are obtained. In the example shown in FIG. 3, since the block size is 4 and the number of words is 8 as described above, the ROM code corresponding to any one of the bit lines B0 to B3 is divided into blocks. As a result, two pieces of blocked data are obtained. For example, if the ROM code corresponding to the bit line B0 is divided into blocks, the block data [0011] corresponding to the word lines W0 to W3 and the block data [1010] corresponding to the word lines W7 to W4 are obtained. (See FIG. 4). Here, the direction of the bit pattern of the blocked data corresponding to the word lines W0 to W3 is the direction from W0 to W3, and the direction of the bit pattern of the blocked data corresponding to the word lines W7 to W4 is W7 to W4.
The direction is toward.

In the next step S18, step S16
For one piece of the blocked data (hereinafter referred to as “current blocked data”) obtained by the above, the type of the blocked data, that is, the bit pattern, is obtained by executing step S16 before that. It is determined whether the block data is the same as the block data. As a result, if the block data is the same as the previous block data, the process proceeds to step S22, and if it is different from any previous block data, the process proceeds to step S20. At this point, there is no previous blocked data, so step S
However, if the blocked data already exists, the process may proceed to step S22.

In step S20, a local netlist describing the configuration of the ROM code circuit (hereinafter referred to as "current circuit block") corresponding to the current block data is created (hereinafter, a net corresponding to one block of data is generated). The list is referred to as a "local netlist"), an identifier is assigned to the local netlist, the identifier is associated with the current blocked data, and the current blocked data is registered. This registration can be performed by storing the current block data in the memory 18 or the hard disk device 12 with a predetermined data structure. In the example shown in FIG. 3, for example, the bit line B0 and the word lines W0 to W
3 is newly created for the block coded data [0011] corresponding to the block coded data [0011], C1 is added to the local net list as an identifier, and the blocked data [0] is added.
011] is registered.

In step S22, in order to indicate the configuration of the current circuit block by the identifier of the local netlist for the registered blocked data of the same type as the current blocked data, the identifier is associated with the current blocked data. No new local netlist is created in step S22.

After executing step S20 or S22,
In step S24, it is determined whether or not the net list for one bit line has been created. If not completed, the process returns to step S18. Then, the step S1
Among the blocked data obtained in step 6, the blocked data not associated with the identifier of the local netlist has a type of the blocked data which is obtained by executing step S16 before. It is determined whether or not it is the same as the data, and the above processing is performed based on the determination result. In the example shown in FIG. 3, in the execution of step S18 this time, the blocked data [10 corresponding to the bit line B0 and the word lines W7 to W4 is
10] is the target of the determination. Then, a local netlist C2 showing the configuration of the ROM code circuit corresponding to the blocked data [1010] is newly created. In the example shown in FIG. 3, as can be seen from FIG. 4, it is determined in step S24 that the creation of the net list for one bit line has been completed.

If it is determined in step S24 that the net list for one bit line has been created, the process advances to step S26 to determine whether the net list for all bit lines has been created. . As a result, if the netlist of any bit line has not been created, the process returns to step S16. in this case,
There is a bit line in which the corresponding ROM code is not blocked, and the same processing as above is performed for one unblocked bit line. In the example shown in FIG. 3, as shown in FIG. 4, at step S18, the current block data [1010] becomes the registered block data, that is, the bit line B0 and the word lines W7 to W4. It is determined to be the same as the corresponding blocked data. As a result, in step S22, the identifier C2 of the already created local netlist is associated with the current blocked data.

In the same manner, steps 16 to S2 are performed until the netlists for all bit lines are completed.
When the process of 6 is repeatedly executed and the netlists for all bit lines are completed, the process proceeds to step S28.

In step S28, the data of the local netlist generated as described above and the data indicating the correspondence between each block data and the local netlist identifier are used to write the entire mask ROM including the decoder and the like. Create a netlist that describes the circuit configuration. That is, while referring to each local netlist by its identifier, a netlist in which the circuit configuration of the entire mask ROM is hierarchically described using the circuit blocks corresponding to each block data as a component is created. In the example shown in FIG. 3, at the time of proceeding to step S28, as shown in FIG. 4, the blocked data [0011], [1010],
Four types of local netlists C1, C2, C3 and C4 corresponding to [ 1111 ] and [ 0000 ] have been created,
In step S28, a netlist is created in which the circuit configuration of the entire mask ROM is hierarchically described with the eight circuit blocks shown in FIG. 4 as constituent elements while referring to these four types of local netlists by the identifiers C1 to C4. To be done.
The netlist created in this way is displayed on the display device 2.
It is displayed at 0 and is output to the hard disk device 12, whereby the netlist generation process is completed.

<Effect> According to the above embodiment, the ROM code circuit is divided into blocks by a predetermined number of bits to obtain the blocked data, and the ROM code corresponding to the blocked data is obtained for each type of the blocked data. A local netlist describing the circuit configuration is generated, and the circuit of the entire mask ROM is hierarchically described with reference to this local netlist. With such a hierarchical description, the amount of data in the netlist can be reduced. For example, for the mask ROM having the configuration shown in FIG. 3, the ROM code is 4
Blocking is done bit by bit to obtain eight blocked data. As shown in FIG. 4, of the eight circuit blocks corresponding to these blocked data, two circuit blocks are local netlists. C1 has the same configuration, the other three circuit blocks have the same configuration as shown by the local netlist C2, and the other two circuit blocks have the same configuration as shown by the local netlist C4. It has the configuration of. Therefore, by the hierarchical description referring to the four types of local netlists C1 to C4, the data amount of the netlist of the ROM code circuit composed of eight circuit blocks is reduced to about four circuit blocks. It can be reduced.

The block size when the ROM code is divided into blocks is selected to be the maximum value of integers within the range of 2 to 16 which is a divisor of the number of words smaller than the number of words. Therefore, relatively large-sized blocked data can be obtained within a range in which the probability that the types of the plurality of blocked data are the same is not significantly reduced. Therefore, the hierarchical description makes it possible to greatly reduce the data amount of the netlist.

<Modification> In the above embodiment, the ROM code corresponding to each bit line is divided into blocks, but the bit lines and the word lines may be replaced with each other. That is, the ROM code corresponding to each word line may be divided into blocks for each plurality of bits, and in that case as well, the data amount of the netlist can be reduced by the hierarchical description as in the above case. In that case, the block size, that is, the number of bits of one block of data is, for example, the maximum number of integers within the range of 2 to 16 that is the number of bits constituting one word, that is, the divisor of the bit width. It may be selected so that it becomes a value.

[Brief description of drawings]

FIG. 1 is a block diagram showing a hardware configuration of a mask ROM data generator that is an embodiment of the present invention.

FIG. 2 is a flowchart showing a part of the operation of the mask ROM data generation device according to the embodiment, which generates a netlist.

FIG. 3 is a circuit diagram showing a configuration example of a ROM code circuit in a mask ROM.

FIG. 4 is a diagram showing how the ROM code circuit shown in FIG. 3 is divided into blocks.

[Explanation of symbols]

10 ... Processing device 16 ... CPU 18 ... Memory B0-B3 ... Bit line W0-B7 ... Word line C1 to C4 ... Local netlist identifier

Claims (2)

(57) [Claims] 1. A mask ROM data generator having a function of inputting a ROM code of a mask ROM, a bit width and the number of words to generate a netlist describing the circuit configuration of the mask ROM, wherein a plurality of ROM codes are provided. Blocking means that collects block-by-bit data collectively for each bit, and for each type of block-blocking data obtained by the block-blocking means, the mask R corresponding to the block-blocking data
Local netlist creating means for creating a local netlist describing the circuit configuration of the OM; and the mask ROM with the circuits corresponding to each of the blocked data as constituent elements while referring to the local netlist.
And an all-area netlist creating means for creating an all-area netlist in which the circuit configuration of the above is hierarchically described. 2. The mask ROM data generator according to claim 1, wherein the blocking unit presets the number of bits of the blocked data to be a divisor of the number of words smaller than the number of words. A mask ROM data generator, wherein the maximum value is an integer less than or equal to the specified value.