JPH04115363A - Logical simulation system - Google Patents

Abstract

PURPOSE:To hold timing information between plural input signals and to accurately attain logical simulation by storing the status change history of a circuit simulation output node which is calculated by a general purpose computer together with a change time and applying the history to an LSI mounted on a part of a circuit. CONSTITUTION:In a simulation system mounting an existing LSI 4 on a part of a circuit element and mounting a general purpose computer 1 on other part, the state change history of the circuit simulation output node calculated by the computer 1 is stored together with the change time in a memory 6 to be a storage means through a control circuit 2 and applied to the LSI 4 to monitor the output terminal of the LSI 4. The LSI 4 can execute accurate simulation by the input of timing information between plural signals without generating malfunction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a logic simulation method, and particularly to a simulation method for logic circuits including existing high-density digital integrated circuits.

[Conventional technology]

2. Description of the Related Art As logic simulations have become more common due to recent advances in semiconductor technology and computer technology, there has been an increasing demand for large-scale circuit simulations, especially circuit simulations involving LSIs.

Conventionally, when performing logic simulation, a device model written in software is required. but,
It is difficult to describe a model of a large-scale LSI such as a microprocessor in software, and it is almost impossible when considering the number of man-hours required for development. Even if developed, evaluation is difficult and simulation requires a large amount of time. As a means to solve such problems, a method is used in which an actual digital element is used as a device model.

[Problem J that the invention seeks to solve]

In the conventional logic simulation method described above, the history of state changes of the output node of the circuit simulation calculated by a general-purpose computer, that is, the state value change information given to the actual LSI, includes only order information and time information. For example, as shown in the actual waveform diagram in Figure 2(a) and the waveform diagram saved as history in Figure 2(b), timing information between multiple input signals is lost. In the worst case, the actual LSI may malfunction, making it impossible to perform accurate logic simulation.

[Means to solve the problem]

The logic simulation method of the present invention is a logic simulation method in which, when simulating a logic circuit including a plurality of circuit elements, a part of the plurality of circuit elements is implemented using an existing LSI, and other parts are simulated by a general-purpose computer. , storage means for storing a history of state changes of output nodes of the circuit simulation calculated by the general-purpose computer together with change times; means for applying the history of the output nodes to the LSI according to the change times; and an output terminal of the LSI. and control means for monitoring the output terminal and returning an output signal of the output terminal to the input node of the circuit simulation when a change occurs at the output terminal.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. The embodiment shown in FIG. 1 includes a general-purpose computer 1, a control circuit 2, and an input register 3.
, LSI 4, output register 5, and input state value storage memory 6
It is composed of:

A general-purpose calculation 1111 executes circuit simulation excluding the LSI 4 using software. When a change occurs in the output node to the LSI 4, an LSI access 101 is output, and the operation of the LSI 4 is determined based on the change output 102 of the LSI 4. The control circuit 2 inputs the LSI access 101, identifies the pin number and input state value, and performs the memory access 10.
8 and input history 10 from the input state value storage memory 6.
9 is input, and control 103 and access control 104 are output. The input history 109 includes state value change information and change time information, and the access control 104 is controlled to reproduce accurate waveforms based on the time information. The input register 3 inputs a control 103 and an access control 104, and outputs a drive output 105. LSI4 inputs control 103 and drive output 105, and outputs response output 1.
Outputs 06. Output register 5 is control 103
is input, the response output 106 of the LSI 4 is monitored, and when a change occurs in the output, the change output is latched, and a change output 107 is output together with time information from after the simulation has started. The input state value storage memory 6 manages the input state values and change time information of each input pin of the LSI 4, and inputs the memory access 108 to store the change information and time of the input state value of the corresponding input pin after the simulation starts. information is output as an input history 109.

〔Effect of the invention〕

As explained above, the present invention provides an output node of a circuit simulation calculated by a general-purpose computer in a logic simulation method in which an existing LSI is mounted on a part of a plurality of circuit elements and the other parts are simulated by a general-purpose computer. A means for storing the history of state changes together with the time of change, and a means for storing the history of the output node according to the time of change.
By having a means for applying the signal to the SI and a means for monitoring the output terminal of the LSI and returning the output signal of the output terminal to the input node of the circuit simulation when a change occurs in the output terminal, calculations can be performed by a general-purpose computer. Since time information is included in the state change history of the output node of the circuit simulation, that is, the state value change information given to the actual LSI, timing information between multiple input signals is saved, and the actual This has the effect that logic simulation can be performed accurately without causing the LSI to malfunction.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a diagram for explaining an example of the problem of a conventional logic simulation method. DESCRIPTION OF SYMBOLS 1... General-purpose computer, 2... Control circuit, 3... Input register, 4... LS1.5... Output register, 6
...Input status value storage memory.

Claims (1)

[Claims] When simulating a logic circuit including a plurality of circuit elements, a portion of the plurality of circuit elements is an existing LSI.
In a logic simulation method in which a circuit simulation is implemented and other parts are simulated by a general-purpose computer, a storage means for storing a history of state changes of an output node of a circuit simulation calculated by the general-purpose computer together with a change time; The history is changed to the LS according to the change time.
monitoring the output terminal of the LSI;
A logic simulation method comprising: control means for returning an output signal of the output terminal to an input node of the circuit simulation when a change occurs in the output terminal.