JPH02252065A - Logical simulation method - Google Patents

Abstract

PURPOSE:To highly accurately and efficiently execute the simulation of the whole logical device by evaluating each individual block or function element constituting a logical device at a previously set different time interval in an event driving type logical simulation system. CONSTITUTION:An event to be generated within a fixed time is read out from the list of events recorded in an event/signal value schedule table 12 and a signal value indicating an event out of signal values stored in an internal state storage means 11 is updated and stored in an event storing means 15. Then, an evaluation timing deciding means 14 counts up respective elapsed time intervals by each unit time and indexes ID numbers and an evaluation condition storing means 13 successively obtains the valuation time intervals and the list of the IDs of the function elements or function blocks corresponding to the intervals. Then, respective IDs are successively inputted to a connecting information storing means 17, whether these IDs are stored in the means 15 or not is decided, and when the IDs are stored, the contents are deleted from the means 15.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to the design of logic devices, including timing,
The present invention relates to a logic simulation method for verifying the functional or logical operation of a logic device.

Conventional technology In recent years, with the progress of integrated circuit technology, LSI or ultra-LSI
By using I, it is possible to realize logic devices that are complex but have relatively low production costs (high added value).However, in the development of such logic devices, there are Therefore, the challenge is to reduce the increasing development and design costs.Furthermore, as the process progresses, modifications and changes become extremely difficult, so improving reliability from the initial stage of design has become a challenge.This background Under these circumstances, emphasis is placed on increasing the accuracy and speed of logic simulations that verify the functional design of logic devices and detailed gate-level logic designs.

In general, a logic device is expressed using a connection relationship between inputs and outputs of functional elements such as logic gates, flip-flops, registers, and counters, or functional blocks that perform more complex operations. In logic simulation, the logic values of the signals in each part of the logic device are determined for each unit time by inputting the specifications of the logic device and a test pattern representing a temporal change in the input signal to the logic device. Conventional logic simulation is performed using a compilation method in which specifications of a logic device are compiled and executed, or an event-driven method (for example, VLS I Design ■, Iwanami Shoten, 1985, pp. 193 to 197). In the compilation method, complicated processing is avoided, and the evaluation procedure and order of each functional element or functional block constituting the logical device are fixed and executed, thereby simplifying and speeding up the processing. However, handling feedback loops and delays becomes difficult. For this reason, recently, many event-driven methods have been adopted, which can be applied to any circuit and are suitable for timing analysis that takes into account flip-flop setup and hold times and clock skew.

In the event driven system, an event indicates which loss signal change of a logic device has occurred. Further, event-driven means to selectively evaluate the functions of functional elements and functional blocks based on the occurrence of the event and the connection relationship inside the logic device. Event-driven logic simulation focuses on changes in signal values on wiring that connects input terminals of a logic device and input/output terminals of functional elements or functional blocks. When and which wiring signal values change is stored in a schedule table. Only when the signal value on the wiring changes, the operation of the functional element or functional block to which the wiring destination is input is evaluated to determine the output signal value and internal state. When the output signal value changes, the wiring through which it propagates and its signal value are stored in a schedule table based on delay information. A simulation is performed by repeating such processing every unit time when an event occurs.

FIG. 10 is a flowchart showing an example of a process for evaluating the operation of a circuit in a simulation for each unit time in the conventional event-driven method as described above. Below, the 10th
The flow of processing will be explained using figures.

First, set the current time to the nearest future time at which the event is scheduled to occur (Step I), read out the event scheduled to occur at that time from the list of scheduled events (Step 2), The value of the signal indicated by the event is updated to the signal value stored in the schedule table (step 3), and then the value of the signal indicated by the event is updated to the signal value stored in the schedule table.Next, the value of the signal indicated by the event is updated to the signal value stored in the schedule table, and then the function element or function to which the event is propagated is A block, ie, a functional element or a functional block to which the signal line whose signal value has changed is connected as an input is selected (step 24). If no functional element or functional block to be evaluated is selected, the next unprocessed event is read (step 25).
). If one or more functional elements or functional blocks are selected, a functional evaluation is performed to calculate an output signal value from the functional specifications and input signal values (step 6). As a result of the evaluation, it is determined whether a new event has occurred in the output signal value of the functional element or functional block (Step 7), and if an event has occurred, it is determined based on the delay information given for each functional element or functional block. The event and the signal value after the change indicated by the event are scheduled (step 8). If no new event has occurred, the next event scheduled to occur at the current time is read out, and the above process is repeated (step 26). When there are no more events scheduled to occur at that time, the current time is set to the nearest future time at which the event was scheduled to occur, and processing moves on to the next unit of time.

Problems to be Solved by the Invention The event-driven method using the method described above is an efficient method in the sense that it selects and evaluates only the operation of the part where the event occurs in the logic device. However, conventional event-driven simulations have the following inefficient aspects.

When simulating the entire logic device, some functional blocks or functional elements that make up the logic device require simulation with high timing accuracy due to differences in design progress and points of focus, but other functions require simulation with high timing accuracy. This is not necessary for blocks or functional elements, and functional simulation is often sufficient. In contrast, in conventional simulation methods, all processes are performed with the same precision, so extra processing time must be spent.

In view of the above problems, the present invention provides a highly accurate and efficient logic simulation method that reduces unnecessary processing in the event-driven method.

Means for Solving the Problems In order to solve the above problems, the logic simulation method of the present invention uses an event-driven method, and is a logic simulation method for a logic device, in which each functional element or As a condition for evaluating internal states and output signal values for functional blocks,
evaluation condition storage means for storing the time interval for executing the evaluation; and monitoring the passage of unit time and outputting data specifying the functional element or functional block for which the evaluation time interval stored in the evaluation condition storage means has elapsed. an event determining means for determining whether an event that drives a functional element or a functional block has occurred using the evaluation timing determining means and selecting a functional element or functional block to be evaluated; an event storage means for storing an article event, the event storage means stores an event that occurs, and the evaluation timing determination means stores an event for which the evaluation timing determination means has elapsed an evaluation time interval specified by the evaluation timing determination means. A logical simulation method characterized by using an image determining means to determine the presence or absence of an event that drives the functional element or functional block, select the functional element or functional block in which the event is stored, and execute the evaluation. It is.

Operation According to the method described above, the present invention can evaluate each functional block or functional element constituting a logic device at different preset time intervals.

This makes it possible to simulate the entire logic device with the necessary precision and efficiency.

Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart showing logical simulation processing for each unit time. FIG. 2 is a flowchart of the process of selecting a functional element or functional block to perform functional evaluation in step 5 of FIG. 1. FIG. 3 is a configuration diagram of a simulator that implements the logic simulation of this embodiment. Fourth
This figure is a block diagram of evaluation condition storage means that constitutes the simulator of FIG. 3. FIG. 5 is a block diagram of the evaluation timing determining means of FIG. 3. FIG. 6 is a block diagram of the event determination means of FIG. 3. FIG. 7 is a diagram showing the functional blocks used in the logic simulation example according to this embodiment and the contents of the evaluation condition storage means. FIG. 8 is a timing chart showing changes in input and output signal values of the functional blocks of FIG. 7 used in the logic simulation example according to this embodiment. FIG. 9 is a diagram showing the internal states of the evaluation timing determining means and the event storing means in the logic simulation example according to this embodiment.

First, the configuration of the simulator of this embodiment will be explained using FIGS. 3, 4, 5, and 6.

In FIG. 3, 10 is a time control means for controlling the progression of simulation time. The current time on the simulation can be referred to by the time control means 10.

Reference numeral 11 denotes an internal state storage means for holding internal states of functional elements and functional blocks constituting the logic device, signal values of input/output terminals, and signal values on wiring. The internal state storage means 11 is a data table that can be searched using the identifiers of functional elements, functional blocks, and wiring as indexes, and that can read and write the internal states and input/output signal values of each.

Reference numeral 12 is an event/signal value schedule table that stores events occurring at respective future times relative to the current time indicated by 10 of the time control means and signal values after their changes. phenomenon·
The signal value schedule table 12 stores signals in which events occur and their signal values using relative times as indexes. Further, in the event/signal value schedule table 12, when the current time is updated by the time control means 10, the relative time at which each future event will occur is updated in synchronization.

Reference numeral 13 denotes evaluation condition storage means for storing time intervals for performing evaluation regarding each functional element or functional block constituting the logical device. The configuration of the evaluation condition storage means 13 is shown in FIG.

Reference numeral 14 denotes an evaluation timing determining means that refers to the evaluation time interval held in the evaluation condition storage means 13 and outputs a signal specifying a functional element or functional block to be evaluated at the current time. The configuration of the evaluation timing determining means 14 is as follows.
As shown in the figure.

15 is an event storage means for storing events. The event storage means 15 is realized by a data table of flags indicating whether or not an event exists for each signal, and input/output means for searching for the presence or absence of an event and deregistering an event.

Reference numeral 16 denotes an event determining means for determining whether an event has occurred in the functional element or functional block specified by the evaluation timing determining means 15. The configuration of the event determining means 16 is shown in FIG.

Reference numeral 17 denotes connection information storage means for storing connection information between functional elements and functional blocks constituting the logical device. The connection information storage means 17 stores a list of input signals connected to each functional element or functional block using the identifier of the functional element or functional block as an index.
That is, it is a data table from which a list of events that drive each functional element and functional block can be searched.

On the 1st, the internal state storage means 11 is stored for each functional element or functional block selected by the event determination means 16.
This function evaluation means evaluates the internal state and output signal value by referring to the current internal state and input signal value held in the controller. The function evaluation means 18 is realized by means for storing the function evaluation procedure for each functional element or functional block, means for executing the same, and a correspondence table between the identifier of the given functional element or functional block, the procedure to be executed, and the same.

19 is the result of the functional evaluation performed by the functional evaluation means 18,
This is an event/signal value scheduling means that schedules events and signal values in the event/signal value schedule table 12 based on delay information when a new event occurs. The event/signal value scheduling means 19 compares the signal value obtained as a result of the functional evaluation by the function evaluation means 18 with the signal value stored in the internal state storage means 9, and determines whether a change in the signal value has occurred. Occurrence of an event based on the comparator and the data storage means for storing the delay time searched using the identifier of each functional element, functional block or wiring as an index, the current time indicated by the time control means 10, and the delay time obtained from the data storage means. It can be constructed from a computing unit that calculates the relative time.

FIG. 4 is a block diagram of the evaluation condition storage means 14 that constitutes the simulator of FIG. 3. In FIG. 4, 141 is
This data storage means stores a list of identifiers of functional elements or functional blocks to be evaluated at equal time intervals in correspondence with the evaluation time intervals.

An identification number for search is set in each item of the data storage means 141. Reference numeral 142 denotes input/output control means for reading out the evaluation time interval or the identifier list of functional elements or functional blocks from the data storage means 141 using the identification number as an index. With the above configuration, it is possible to determine which functional element or functional block is to be evaluated at each time interval given as an evaluation condition.
can be obtained via the identification number.

FIG. 5 is a block diagram of the evaluation timing determining means 15 of FIG. 3. In FIG. 5, reference numeral 151 indicates the time from which each functional element and functional block was most recently evaluated for each identification number given to each evaluation time interval and the identification number in the data storage means 141 of FIG. It is a data storage means for storing elapsed time intervals. 152 is a counting means that counts up each elapsed time interval of the data storage means 151 by one unit time using the count up signal as a trigger.

Reference numeral 153 denotes input/output control means that inputs the identification number and evaluation time interval, searches the data storage means 151, performs data collation, and outputs a selection signal 155 to the selector 154. The input/output control means 153 compares the elapsed time interval of the item having the identification number matching the input with the evaluation time interval of the input. If the comparison results match, the elapsed time interval is reset to O and 1 is output to the select signal 155. If they do not match, 0 is output to the select signal 155. A list of identifiers of functional elements or functional blocks corresponding to the identification numbers input to the input/output control means 153 is input to the selector 154 , and
When the select signal 155 output by is 1, the input list is output. When the select signal 155 is O, data indicating that there is no selected identifier is output.

FIG. 6 is a block diagram of the event determination means 16 of FIG. 3.

A buffer 161 sequentially outputs each identifier from a list of identifiers of functional elements and functional blocks. 162 is
This is an event checking means that compares the event list output from the connection information storage means 17 and the event list stored in the event storage means 15. If at least one event in the event list output by the connection information storage unit 17 is stored in the event storage unit 15, the event matching unit 162 outputs 1 to the select signal 165, and simultaneously selects the corresponding event. is deleted from the event storage means 15. If no event in the event list output by the connection information storage means 17 is stored in the event storage means 15, O is output to the select signal 165. When the select signal 165 is 1, the selector 163 transfers the identifier output from the buffer 161 to the buffer 1.
64. When the select signal 165 is 0, data indicating that there is no selected identifier is output.

Next, the flow of the logical simulation processing for each unit time of this embodiment will be explained using mainly FIGS. 1 and 2.

First, the current time is set to the nearest future time at which the event is scheduled to occur (step 1). From the list of events scheduled in the event/signal value schedule table 12, the event scheduled to occur at that time is read out. Step 2): Among the signal values stored in the internal state storage means 10, the signal value indicated by the event is read out. is updated to the signal value stored in the event/signal value schedule table 12 (step 3). The event is stored by the event storage means 15 (
Step 4), and then select a functional element or functional block to be evaluated based on the functional evaluation time interval and the presence or absence of an event (step 5).

The process of step 5 will be explained using FIG.

First, each elapsed time interval stored in the evaluation timing determining means 14 is counted up by one unit time (
Step 51) Next, using the identification number as an index, the evaluation condition storage means 13 sequentially obtains a list of evaluation time intervals and identifiers of functional elements and functional blocks corresponding thereto. For each set of the obtained identification number, evaluation time interval, functional element, and functional block, the evaluation timing determining means 14 is used to select the identifier list of the functional element or functional block for which the evaluation time interval has elapsed ( Step 52).

Each identifier in the identifier list of each functional element or functional block selected in step 52 is input in sequence into the connection information storage means 17 to obtain a list of events that drive the functional element or functional block indicated by the identifier (step 53).

For each event list, the event matching means 162 determines that at least one event in the event list is detected by the event matching means 5.
It is determined whether or not it is stored in (step 54).

If at least one event in the event list is stored in the event storage means 15, the selector 163 selects
The identifier of the functional element or functional block corresponding to the event list is selected (step 56). At the same time, the events in the event list are deleted from the event storage means 15 (
Step 57). This concludes the explanation of step 5 in FIG. 1, and next, explanation will be given from step 6.

Functional evaluation of the functional element or functional block indicated by the identifier selected in step 5 is performed using the functional evaluation means 18 (step 6).

As a result of the evaluation, if no new event has occurred, the simulation for that unit time is ended and the simulation proceeds to the next unit time (step 7). When a new event occurs, the event and signal value are scheduled in the event/signal value schedule table 11 by the event/signal value scheduling means 18 (step 8), and the process ends (step 9).

Next, an example of logic simulation using the simulation method of this embodiment will be explained using mainly FIGS. 7, 8, and 9.

FIGS. 7(a) and 7(b) are data diagrams for storing functional blocks to be simulated and their evaluation conditions.

In FIG. 7, 20 is a functional block that inputs two 8-bit signals A and B, performs multiplication, and outputs a 16-bit signal C. The functional block 20 is given the number 1 as an identifier. 1411 is functional block 2
11 shows a data table in an evaluation condition storage means that stores evaluation conditions of 0. In the evaluation condition of the identification number i of the data table 1411, T as the evaluation time interval and a list of identifiers including the identifier 1 of the functional block 20 are stored.

FIG. 8 is a timing chart showing events occurring in the input signal of the functional block 20 and events occurring in the output signal resulting from functional evaluation. 21 is functional block 2
This indicates that an event has occurred at time 0 for input signal B of 0. Similarly, in 22, an event occurs in the input signal A at time t1,
In 23, event 21.22 indicating that an event occurs in the output signal C at time t2 is registered in advance by the event/signal value scheduling means as an event occurring at time to and time t1 in the event/signal value schedule table, respectively. Suppose that

FIG. 9 shows the elapsed time interval between the event stored in the event storage means and the identification number i in the data table of the evaluation timing determination means at each time in the timing chart of FIG.

13L 132.133.134.135°136 is
Events stored in the event storage means at time 1, time to, time t1, time T, time t2, and time 2T in the timing chart of FIG. 8 are shown, respectively. 1511.1512
．． 1513.1514.1515.1516 are time 1 and time LO1 in the timing chart of FIG. 8, respectively.
The elapsed time intervals of the item having the identification number i in the data table of the evaluation timing determining means at time L1, time T, time t2, and time 2T are shown.

Using the above, a simulation process from time 1 to time 2T for the functional block 20 with the specified evaluation time interval T will be described.

First, at time 1, the elapsed time interval 1511 of the identification number i is set to 1 as an initial setting, and no event is stored in the event storage means 131. Events and events until time to
Since the event is not registered in the signal value schedule table,
The current time is updated by only counting up one unit of time for each elapsed time interval in the data table of the evaluation timing judgment and determination means. At time to, input signal B of function block 20
event 21 is read out from the event/signal value schedule table, and the signal value of signal B stored in the internal state storage means is updated. Event 21 is stored by the event storage means.

The contents of the event storage means are as shown in FIG. 9, 132.

Each elapsed time interval in the data table of the evaluation timing determining means is counted up by one unit time.

Next, a process of searching a list of identifiers of functional elements and functional blocks for which the evaluation time interval has elapsed by the evaluation timing determining means will be described. First, data table 1 of evaluation condition storage means.
In step 411, an identifier list of functional elements and functional blocks including the identification number i, its evaluation time interval T, and the identifier 1 of the functional block 20 is obtained. The evaluation timing determining means determines the function block 2 from the identification number I and the evaluation time interval T.
It is determined whether a list of identifiers including 0 and 1 is to be selected. In this case, the value of elapsed time interval 1512 is t.

Since the evaluation time interval T has not elapsed, the list of identifiers including identifier 1 of this functional block 20 is not selected. This completes the simulation process for time to, and updates the current time.

Thereafter, in the processing at each time up to time t1, each elapsed time interval in the data table of the evaluation timing determining means is counted up by one unit time. At time t1, function block 2
Event 22 of input signal A of 0 is read from the event/signal value schedule table. Processing is carried out in the same manner as in the case of time LO, and event 22 is stored by the event storage means. The contents of the event storage means are as shown in FIG. 9, 133.

Similarly, in processing each time up to time T, each elapsed time interval in the data table of the evaluation timing determining means is counted up by one unit time. At time T, each elapsed time interval in the data table of the evaluation timing determining means is counted up by one unit time, and the elapsed time interval of identification number i becomes T. Next, the identification number i is entered from the data table 1411 of the evaluation condition storage means.
and its evaluation time interval T, the functional element including the identifier 1 of the functional block 20, and the identifier list of the functional block are obtained, and the evaluation timing determining means calculates the identifier including the identifier 1 of the functional block 20 from the identification number i and the evaluation time interval T. Determine whether to select a list of identifiers.

In this case, since the evaluation time interval T has elapsed, the identifier list of functional elements and functional blocks including the identifier 1 of the functional block 20 is selected. At the same time, the elapsed time interval of the identification number i in the data table of the evaluation timing determining means is reset to O. The elapsed time interval of identification number i at time T is
The result will be as shown in FIG. 9 1515.

Next, each identifier in the identifier list is selected by the event determining means. The selection of the identifier l of the functional block 20 by the event determination means is performed as follows.

First, a list of events that drive the functional block 20 is obtained by the connection information storage means. Assume that the event list is obtained from the input signal names A and B from the block diagram of FIG. Next, the event checking means determines whether at least the negative event in the event list is stored in the event storage means.

In this case, since ASB is also stored as an event in the event storage means, identifier 1 of the functional block 20 is selected. At the same time, events A and B in the event list are deleted from the event storage means. As a result, the contents of the event storage means become as shown in FIG. 9 134.

When an identifier is selected, a functional evaluation means performs a functional evaluation of the functional element or functional block corresponding to the identifier.

For identification number 1, the evaluation procedure of function block 20 is activated and output signal C is calculated. At this time, in this simulation example, it is found that the signal value changes on the signal line C, and a new event is registered in the event/signal value schedule table at the delay time given to the functional block 20.

This completes the simulation process for time T, and updates the current time.

Subsequently, in processing each time up to time L2, each elapsed time interval in the data table of the evaluation timing determining means is counted up by one unit time. At time t2, function block 2
Event 22 of output signal C of 0 is read from the event/signal value schedule table. Processing is performed in the same manner as at time to, and event 22 is stored by the event storage means. The contents of the event storage means are as shown in FIG. 9, 135.

In processing each time up to time 2T again, each elapsed time interval in the data table of the evaluation timing determining means is counted up by one unit time. Finally, at time 2T, as in the case of time T, each elapsed time interval in the data table of the evaluation timing determining means is counted up by one unit time, and the elapsed time interval of identification number i becomes T. Next, the identification number i and its evaluation time interval T are obtained from the data table 1411 of the evaluation condition storage means.
, a list of identifiers of functional elements and functional blocks including the identifier 1 of the functional block 20 is obtained. The evaluation timing determining means determines whether to select the list of identifiers including the identifier 1 of the functional block 20 from the identification number i and the evaluation time interval T, and since the evaluation time interval T has elapsed,
An identifier list of functional elements and functional blocks including the identifier 1 of the functional block 20 is selected. In this case, since neither ASB of the event that drives the functional block 20 is stored in the event storage means, the simulation is ended without functional evaluation of the functional block 20.

Effects of the Invention As described above, the present invention is an event-driven logic simulation method that evaluates each functional block or functional element constituting a logic device at different time intervals set in advance. The entire logic device can be simulated with the necessary precision and efficiency.

This reduces the time required to verify the functional and logical design of logical devices, including LSIs, which are becoming increasingly large in scale, enabling high-quality designs from the system level and shortening the overall design period. it is conceivable that.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the logic simulation process for each unit time in the logic simulation method according to an embodiment of the present invention, and FIG. 2 shows the functional elements that perform the functional evaluation in step 5 of FIG. Alternatively, FIG. 3 is a flow chart of a process for selecting a functional block, FIG. 3 is a block diagram of a logic simulator that implements a logic simulation method according to an embodiment of the present invention, and FIG. Diagram,
5 is a block diagram of the evaluation timing determining means, FIG. 6 is a block diagram of the event determining means, and FIG. 7 is a functional block to be simulated and its evaluation in an example of logic simulation according to an embodiment of the present invention. 8 is a data diagram for storing conditions, and FIG. 8 is a timing chart showing events occurring in the input signal of the functional block in FIG. 7 and events in the output signal resulting from functional evaluation. FIG. FIG. 10 is a diagram showing the elapsed time interval between the event stored in the event storage means and the identification number i of the data table of the evaluation timing determination means at each time in the timing chart of FIG. 3 is a flowchart showing logical simulation processing at each time. 10... Time control means, 11... Internal state storage means, 12... Event/signal value schedule table, 13... Evaluation condition storage means, 14・・・
...Evaluation timing determining means, 15...Event storage means, 16...Event determining means, 17...
... connection information storage means, 18 ... function evaluation means, 19 ... event/signal value scheduling means. Channel map 2nd map; 4th, 1IJ- Figure! 2-cho tin diagram time t + time time ta 2 Tsubama 2-cho

Claims (1)

[Claims] In a method for performing logic simulation of a logic device using an event-driven method, the above-mentioned evaluation is performed as a condition for evaluating the internal state and output signal value for each functional element or functional block that constitutes the logic device to be simulated. an evaluation condition storage means for storing a time interval for performing the evaluation, and an evaluation for monitoring the passage of unit time and outputting data specifying the functional element or functional block for which the evaluation time interval stored in the evaluation condition storage means has elapsed. a timing determination means; an event determination means for determining whether an event that drives a functional element or a functional block has occurred using the evaluation timing determining means and selecting a functional element or functional block to be evaluated; and an event storage means for storing an event that occurs, the event storage means stores an event that occurs, and the event judgment is performed for a functional element or functional block for which an evaluation time interval specified by the evaluation timing judgment means has elapsed. A logic simulation method characterized in that the presence or absence of an event that drives the functional element or functional block is determined using means, and the functional element or functional block in which the event is stored is selected and evaluated.