JP2980134B2 - Blocked circuit simulation apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] In a circuit simulation of a VLSI circuit design, a block circuit simulation apparatus which divides a circuit to be analyzed into a plurality of partial circuits and simulates each partial circuit. A partial circuit creating means for creating a plurality of partial circuits by dividing the circuit to be analyzed, for the purpose of executing the simulation under conditions close to the actual operation and accurately analyzing the entire target circuit; Equivalent circuit replacement means for searching for a partial circuit and replacing each with an equivalent circuit, wherein the search for the partial circuit is performed only for elements that are directly affected by a signal of an external node of the partial circuit. When performing a simulation of a specific partial circuit, the equivalent circuit replaced as another partial circuit connected to the specific partial circuit. Use configured to and a simulation executing unit for executing a simulation of the specific partial circuit.

[Industrial applications]

The present invention relates to a blocked circuit simulation apparatus and method, in particular, in a circuit simulation of VLSI circuit design, the analysis target circuit is divided into a plurality of partial circuits,
The present invention relates to a block circuit simulation device that performs a simulation for each partial circuit.

In recent years, VLSI circuit design has been steadily increasing in scale, and simulation of the entire chip has become impossible due to limitations on the amount of data. Therefore, a circuit to be analyzed is functionally divided into several blocks and simulation processing is performed for each block (blocked circuit simulation). At this time, there is a demand for a block circuit simulation apparatus having a function of generating an equivalent circuit connected to a circuit to be analyzed, as a pre-process of circuit simulation in VLSI circuit design.

[Conventional technology]

FIG. 5 is a diagram for explaining processing in a conventional block circuit simulation apparatus. As shown in FIG. 3A, the analysis target circuit (VLSI) 4 has a large circuit scale, and is divided into three partial circuits 4a, 4b, and 4c, and simulation is performed for each partial circuit. Has become. Here, there is a network connection between the divided partial circuits 4a, 4b, 4c, and each of the partial circuits (for example, the partial circuit
4a) has an external node directly connected to other partial circuits (4b, 4c) and a power supply (Vcc). Specifically, reference numerals a0 to a5, b0 to b5, c0 to c5 are partial circuits 4a, 4b, respectively.
4c is an external node.

By the way, for example, when analysis (simulation) is performed on the partial circuit 4a (circuit a), conventionally,
It is designed to execute only 4a separately. That is, the simulation is performed with all the external nodes a0 to a5 in the partial circuit 4a disconnected (open state).

[Problems to be solved by the invention]

As described above, in the conventional block circuit simulation apparatus, when the simulation of the partial circuit (4a) obtained by dividing the analysis target circuit 4 is performed, the partial circuit (4a) is used.
Only a) is separated, and the simulation is executed with all the external nodes (a0 to a5) in an open state.

Therefore, with respect to the analysis target circuit 4 composed of blocks (sub-circuits 4a, 4b, 4c) operating under a large interaction, a correct signal waveform could not be obtained and accurate circuit simulation could not be performed. Because, in the actual operating state, for example, the output signal of the partial circuit 4a drives the other partial circuits 4b and 4c,
Is driven by the other partial circuits 4b and 4c. That is, the partial circuit 4a
The other circuits 4b and 4c are mutually affected via a0 to a5, and other circuits connected to external nodes cannot be ignored at the time of simulation execution.

The present invention has been made in view of the above-mentioned problems of the conventional block circuit simulation technology, and has as its object to execute simulation of each partial circuit under conditions close to actual operation and accurately analyze the entire target circuit. .

[Means for solving the problem]

FIG. 1 is a block diagram showing the principle of a block circuit simulation apparatus according to the present invention.

According to the first embodiment of the present invention, a search is made for the partial circuit creating means 1 for dividing the analysis target circuit 4 to create a plurality of partial circuits 4a, 4b, 4c, and for each of the partial circuits 4a, 4b, 4c. Equivalent circuit replacing means 2 for replacing each of the partial circuits with an equivalent circuit, wherein the search for the partial circuit is limited to elements directly affected by a signal of an external node of the partial circuit, and a specific circuit. When simulating the partial circuit 4a,
Simulation execution means 3 for executing a simulation of the specific partial circuit 4a using the replaced equivalent circuit as other partial circuits 4b and 4c connected to the specific partial circuit 4a, Circuit replacement means 2
Replaces the counter node of the capacitor directly connected to the signal input external node with the ground node in the partial circuit performing the search, and replaces all the elements connected earlier from the capacitor with the ground node. For the external node for signal output, all elements connected to the external node for signal output are deleted and a voltage source is added, and for the external node for power supply, the external node for power supply is directly connected to the external node for power supply. A block characterized by replacing a connected resistor with a current source and deleting all elements connected earlier from the resistor so that a partial circuit for performing the search is replaced with an equivalent circuit. An apparatus for simulating an integrated circuit is provided.

Further, according to a second aspect of the present invention, there is provided a block circuit simulation method for dividing a circuit to be analyzed into a plurality of partial circuits and performing a simulation on each of the partial circuits. Inputting data, extracting hierarchical information, capacitance elements, transistor elements, and resistance element information in each of the built-in partial circuits, recognizing connection information between the partial circuits, For the input external node, the opposite node of the capacitor directly connected to the signal input external node is replaced with a ground node, all the elements connected earlier from the capacitor are deleted, and the signal output external node is Removes all elements connected to the signal output external node, adds a voltage source, and
For the power supply external node, a resistor directly connected to the power supply external node is replaced with a current source, and a conversion is made so that all the elements connected earlier from the resistor are deleted to create an equivalent circuit. A method of simulating a blocked circuit is provided in which another partial circuit connected to the partial circuit to be simulated is replaced with the equivalent circuit, and each of the partial circuits is independently simulated.

(Operation)

According to the block circuit simulation apparatus according to the first embodiment of the present invention, the analysis target circuit 4 is divided into a plurality of partial circuits 4a, 4b, and 4c by the partial circuit creation unit 1, and each of the partial circuits is divided by the equivalent circuit replacement unit 2. The circuits 4a, 4b, and 4c are searched and replaced with equivalent circuits. Here, equivalent circuit replacement means 2
The search for the partial circuit in is performed only on the elements directly affected by the signal of the external node of the partial circuit. Then, the equivalent circuit replacing means 2 replaces the counter node of the capacitor directly connected to the signal input external node with the ground node in the partial circuit to be searched, All connected elements are deleted, for the signal output external node, all the elements connected to the signal output external node are deleted and a voltage source is added, and for the power supply external node, By replacing the resistor directly connected to the power supply external node with a current source and deleting all the elements connected earlier from the resistor, the partial circuit for performing the search is replaced with an equivalent circuit. I have.

In addition, a method for simulating a blocked circuit according to a second embodiment of the present invention divides a circuit to be analyzed into a plurality of partial circuits and performs a simulation on each of the partial circuits. Is input, hierarchical information, capacitance element, transistor element, and resistance element information in each of the built-in partial circuits are extracted, and connection information between the partial circuits is recognized. In each partial circuit,
For a signal input external node, a counter node of a capacitor directly connected to the signal input external node is replaced with a ground node, all elements connected earlier from the capacitor are deleted, and a signal output For the external node, all elements connected to the signal output external node are deleted and a voltage source is added. Further, for the power supply external node, the voltage is directly connected to the power supply external node. Is replaced with a current source, and conversion is performed so as to delete all the elements connected earlier from the resistor to create an equivalent circuit.
The other partial circuits connected to the partial circuit to be simulated are replaced with equivalent circuits, and each partial circuit is independently simulated.

This makes it possible to execute a simulation of each partial circuit under conditions close to the actual operation, and to accurately analyze the entire target circuit.

〔Example〕

Hereinafter, an apparatus and method for simulating a blocked circuit according to the present invention will be described with reference to the drawings.

FIG. 2 is a view for explaining characteristic processing in the blocked circuit simulation apparatus of the present invention. FIG. 2 (a) is similar to FIG. 5 (a), and the analysis target circuit (VLSI) 4 is divided into three partial circuits 4a, 4b, 4c because the circuit scale is large. Simulation is performed for each partial circuit. Here, there is a network connection between the divided partial circuits 4a, 4b, 4c, and each partial circuit (for example, the partial circuit 4a) is connected to another partial circuit (4b, 4c), a power supply (Vcc), and the like. It has a directly connected external node. Specifically, reference numerals a0 to a5, b0 to b5,
c0 to c5 are external nodes in the partial circuits 4a, 4b, and 4c, respectively.

Here, as shown in FIG. 2 (b), the partial circuit 4a
Paying attention to (circuit a), reference numerals a3 and a4 are signal input external nodes, reference numerals a1, a2 and a5 are signal output external nodes, and reference numeral a0 is a power supply external node.

By the way, in order to accurately analyze a target circuit, for example, it is necessary to determine how a specific partial circuit 4a to be simulated affects other circuits (subcircuits 4b and 4c) connected to the partial circuit 4a. Need to be analyzed. For that purpose, all circuits must be simulated collectively, which is inconsistent with blocking. Therefore, the range of tracking (load search) to another circuit is basically limited to elements directly affected by the signal of the external node of the circuit (partial circuit). That is, rules for replacing with an equivalent circuit are determined in advance in the program, and an equivalent circuit is generated by the elements picked up by the load search and the automatically generated voltage source elements and current source elements. At this time, in some cases, the search may be further continued.

FIG. 3 is a diagram showing conversion rules of equivalent circuits in one embodiment of the blocked circuit simulation apparatus of the present invention. As shown in the figure, for example, in the sub-circuit 4a performing the search, first, for the signal input external nodes a3 and a4, the opposite node of the capacitance directly connected to the signal input external nodes is connected to the ground node. And all the elements connected earlier from the capacitor are deleted. Next, for the signal output external nodes a1, a2, and a5, all elements connected to the signal output external nodes are deleted and a voltage source is added.
Then, for the power supply external node a0, the resistance directly connected to the power supply external node is replaced with a current source, and all the elements connected earlier from the resistance are deleted. Here, the same conversion processing is performed for the other partial circuits 4b and 4c. Thus, in each partial circuit, conversion to an equivalent circuit is performed according to the type of the external node in the partial circuit.

When the simulation of the specific partial circuit 4a is performed, the other partial circuits 4 connected to the specific partial circuit 4a are
As the b and 4c, the simulation of the specific partial circuit 4a is performed using the equivalent circuit obtained by the above-described method.

FIG. 4 is a diagram for explaining an example of processing in the blocked circuit simulation apparatus of the present invention. In the figure, the blocked circuit simulation program inputs data (circuit data) of the target circuit 4 divided into a plurality of partial circuits 4a, 4b, 4c in step 51. Next, in step 52, a connection state in each of the partial circuits 4a, 4b, and 4c and a network between the partial circuits 4a, 4b, and 4c are recognized, and a netlist is created. Stored in table 63. That is, the input external node, the output external node, and the power supply external node of the equivalent circuit addition target circuit are recognized,
The net information is stored in the netlist table 63.
Here, a detailed instruction for equivalent circuit conversion (control data 61) is given to the control means 62 by a control card or the like, and the detailed instruction for equivalent circuit conversion is recognized and stored in an internal table. That is, an appropriate voltage source is attached to the output external node, and an appropriate current source is attached to the power supply external node. Here, for the partial circuit for which the simulation has already been executed, the signal waveform of the voltage source is automatically obtained from the signal value obtained by the execution (output external node),
Alternatively, the signal waveform of the current source may be automatically obtained from the current value of the resistor obtained by the execution (power supply external node).

Further, in step 53, according to the element pick-up condition, the load of the input external node is searched to generate an equivalent circuit. The equivalent circuit data corresponding to the type of each external node is stored in the equivalent circuit data storage means 64. Also,
The generated equivalent circuit may be given an automatically generated name and added to the original circuit.

Next, in step 54, a simulation execution circuit is created. The simulation execution circuit includes, for example, a specific partial circuit 4a for performing a simulation, and other partial circuits 4b and 4 connected to the specific partial circuit 4a.
An equivalent circuit is connected as c, and is created in accordance with the control data 61 given via the control means 62.

Then, in step 55, the simulation of the simulation execution circuit created in step 54 is executed.

As described above, the blocked circuit simulation apparatus of the present invention allows a program to automatically recognize a connection state in a partial circuit and a network between the partial circuits, and to connect another partial circuit to an external node of a specific partial circuit to be simulated. Is replaced by an equivalent circuit, so that the designer can automatically generate an equivalent circuit and obtain a correct signal waveform only by instructing a program on conditions for picking up elements.

〔The invention's effect〕

As described above in detail, according to the present invention, the simulation of the partial circuits to be simulated is performed in a state where the appropriate equivalent circuits corresponding to the surrounding partial circuits are connected, so that the simulation of each of the partial circuits is actually performed. Can be executed under conditions similar to the above operation, and the entire target circuit can be accurately analyzed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the principle of a blocked circuit simulation device according to the present invention, FIG. 2 is a diagram for explaining characteristic processing in the blocked circuit simulation device of the present invention, and FIG. FIG. 4 is a diagram showing an equivalent circuit conversion rule in one embodiment of the block circuit simulation apparatus of the present invention. FIG. 4 is a view for explaining an example of processing in the block circuit simulation apparatus of the present invention. FIG. FIG. 4 is a diagram for explaining processing in the integrated circuit simulation device. (Explanation of reference numerals) 1... Partial circuit creation means 2... Equivalent circuit replacement means 3... Simulation execution means 4... Analysis target circuits 4 a, 4 b, 4 c.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yukihisa Shioda 2-1844-2 Kozoji-cho, Kasugai-shi, Aichi Fujitsu VSI Co., Ltd. (56) References JP-A-3-105567 (JP, A) JP-A Sho 62-182972 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G06F 17/50 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A partial circuit creating means for dividing a circuit to be analyzed to create a plurality of partial circuits, and an equivalent circuit replacing means for searching for each partial circuit and replacing each partial circuit with an equivalent circuit. The search is limited to elements directly affected by the signal of the external node of the partial circuit, and when a specific partial circuit is simulated, the other connected to the specific partial circuit Simulation executing means for executing a simulation of the specific partial circuit using the replaced equivalent circuit as a partial circuit, wherein the equivalent circuit replacing means includes: On the other hand, the opposite node of the capacitor directly connected to the signal input external node is replaced with a ground node, and the element connected earlier from the capacitor is replaced with the ground node. For a signal output external node, all elements connected to the signal output external node are deleted to add a voltage source, and for a power supply external node, the power supply external node is connected to the power supply external node. It is characterized in that a directly connected resistor is replaced with a current source, and all elements connected earlier from the resistor are deleted, so that a partial circuit for performing the search is replaced with an equivalent circuit. Blocking circuit simulation device. 2. The circuit to be analyzed is divided into a plurality of partial circuits.
A block circuit simulation method for performing a simulation for each of the partial circuits, comprising: inputting circuit data of each of the partial circuits; Extracting element information, recognizing connection information between the respective partial circuits, and connecting each of the partial circuits to a signal input external node by connecting a counter node of a capacitor directly connected to the signal input external node to a ground node; In addition, remove all the elements connected earlier from the capacitor, remove all the elements connected to the signal output external node for the signal output external node, and add a voltage source, and For a power supply external node, a resistor directly connected to the power supply external node is replaced with a current source, and all elements connected earlier from the resistor are deleted. And converting the other partial circuits connected to the partial circuit to be simulated to the equivalent circuit, and simulating each of the partial circuits independently. Circuit simulation method.