JP2785762B2 - Fan-out check device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a logical design rule checking device, and more particularly to a fan-out checking device in which a check standard can be changed according to operating conditions.

[0002]

2. Description of the Related Art A fan-out check defined in the present invention is defined as one of output units connected to each net.
Focusing on the above, this means a function of comparing the drive capacity value of the output section with the total capacity of the nets connected to the net, and determining whether the drive capacity value of the output section is appropriate.

This check prevents an unnecessarily large driving capacity, that is, a large-scale element from being used at the time of designing the LSI, thereby preventing the area of the entire LSI from becoming unnecessarily large and satisfying the actual driving capacity. This is performed for the purpose of finding such an element at an early stage of the design in order to prevent the use of a non-existing element and causing a malfunction.

[0004] The terms used below are defined as follows.

"Net": A wiring for connecting terminals of a plurality of elements.

"Element": One unit constituting a semiconductor integrated circuit. For example, a NOT circuit, an AND circuit, an OR circuit, a NAND circuit, a NOR circuit, and the like.

"Net capacitance": A numerical value representing the impedance when a current passes through a net.

"Total net capacitance": The total value of the capacitance added to the input terminals or bidirectional terminals of all the elements connected to the net.

"Input capacitance": A numerical value representing the impedance of the input terminal.

[0010] "Drive capacity": limit value of the capacity that can be connected to the output terminal.

"Capacity" means impedance.

FIG. 6 shows a conventional fan-out check device.
As shown in (1), the configuration includes a circuit information file, a fan-out check information file, a fan-out check calculation unit, and a result file. FIG. 7 is a flowchart showing the operation performed by the fan-out check calculator 27 in FIG. Hereinafter, a flowchart performed in the conventional fan-out check will be described.

The process is started by a process 29 and a process 30
Input the circuit information file. In the circuit information file 25, a logic circuit configuration diagram of the semiconductor integrated circuit to be subjected to the fan-out check is stored as data. Here, a part of the logic circuit is shown in FIG. 4 and will be described as an example. .

In the process 31, all the input units connected to the net 21, that is, the input capacities of the input units 23 and 24 and the net capacity of the net 21 are obtained from the fan-out check information file 26. In the fan-out check information file 26, input capacities of elements generally used in semiconductor integrated circuits, drive capacity reference values, capacities per unit length of nets, and the like are stored in advance. Next, processing 32
Then, the input capacity and the net capacity are added to calculate the total net capacity.

In a process 33, a standard value of the drive capability of the output unit connected to the net is obtained from the fan-out check information file 26.

Under the condition 34, the net total capacity calculated at 32 is compared with the output drive capacity value obtained at 33. If the total net capacity is equal to or less than the output drive capacity value, it is determined in step 35 that it is OK, otherwise it is determined that it is NG in step 36, and the processing determination result is output to the result file 28.

Since there are usually a plurality of nets in a logic circuit, it is determined whether or not all nets have been compared according to the condition 37. If all the nets have been compared, the process ends in step 38; otherwise, the process returns to step 34. .

If the result of the processing determination is NG, that is, if there is an undesired connection relation in the operation of the semiconductor integrated circuit, a fan-out check is performed again after the circuit is modified.

[0019]

In the above-described conventional fan-out check, the information of the output unit drive capability value stored in advance in the fan-out check information file 26 by the manufacturer of the fan-out check device is determined by all users. Semiconductor integrated circuits in the environment, ie LS
LS means that its operation is guaranteed even if I is used.
The value when operating I under the most severe operating conditions, that is, the worst value has been given as information. The worst value is determined by referring to three factors that determine the driving capability of the element, that is, the operating frequency, the operating voltage, and the operating temperature. In general, the value when the operating frequency is high, the operating voltage is low, and the operating temperature is high is virtually the worst value, and this worst value is a value that is significantly smaller than the drive capability value under normal operating conditions of the element. Becomes

Accordingly, under actual operating conditions, for example, although the element A having a small driving ability is sufficient, the driving ability of the element A is not sufficient in the fan-out check, and the circuit needs to be reviewed. For example, the element B having a higher driving capability than the element A, for example, is selected. However, the worst value is obtained for the element B in the fan-out check, but in an actual operation, the driving performance may be higher than the worst value. At this time, there is no problem in the operation of the circuit because the driving capability is larger than the net total capacitance, but there is generally no problem in an element having a large driving capability, and therefore the area of the circuit is increased. Therefore, in today's demand for downsizing of the circuit, the driving capability of the element is slightly larger than the total net capacitance, and there is no need to stick to the worst value.

Also, if the semiconductor maker prepares a drive capacity value corresponding to a general operating environment other than the worst environment, on the contrary, the actual drive capacity is satisfied under the worst environment or an operating environment worse than the general environment. There is a possibility that an element that does not have a failure in the fan-out check and will not operate properly.

[0022]

According to the fan-out check device of the present invention, the drive capacity and the total net capacity of each net are compared for each net, and whether or not the net capacity connected to the net is appropriate. In the fan-out check function to make a judgment, a function to calculate the drive capacity based on three data: parameter data corresponding to the operating environment prepared in advance by the manufacturer, drive capacity reference value data of the output unit, and operating environment data input by the user. It is characterized by having.

[0023]

The fan-out check device of the present invention is the most suitable in the actual operating environment of each element of the semiconductor integrated circuit to be fan-out checked, based on the parameter data prepared in advance and the operating environment data input by the user. The driving ability value can be calculated.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fan-out check device according to the present invention has a configuration as shown in FIG. That is, the difference from the conventional one is that the fan-out check calculation unit further includes a parameter file in which parameters corresponding to various operating environments are stored, and operating environment information input by a user. Is that the driving capability is calculated. FIG. 2 is a flowchart illustrating an operation performed by the fan-out check calculation unit in FIG. FIG.
Is a part of the logic circuit described in the circuit information file 1, and the processing in the middle will be described using this circuit diagram as an example.

After starting by the process 8, the semiconductor integrated circuit (LS) to be subjected to the fan-out check by the process 9
The circuit information of I) is input from the circuit information file.

In step 10, the input capacities and net capacities of all input units connected to the net are obtained from the fan-out check information file 2. Next, the input capacity and the net capacity obtained in the process 10 are added in the process 11 to calculate the total net capacity. This operation will be described with reference to the example of FIG.
3. The input capacity of the input unit B24 connected to the net and the net capacity of the net 21 are obtained from the fan-out check information file 2. Next, in process 11, the input capacity and the net capacity are added to calculate the total net capacity.

In the process 12, information on the drive capability standard value of the output unit 22 connected to the net, that is, the drive capability value preset by the fan-out check device maker is obtained from the fan-out check information file 2.

In the process 13, information 4 on the operating environment is obtained from the user. This means that the fan-out check device obtains information from the user by means such as keyboard input. The process 13 will be described with reference to FIG. 5, which is an example of the parameters input here. As the information on the operating environment, the operating frequency A, operating voltage E, and operating temperature I shown in FIG. 5 are obtained from the user.

The processing 14 compares the operating environment obtained from the user with the parameter file 3 corresponding to the operating environment, and obtains parameters corresponding to the operating environment obtained from the user. The parameter file 3 is prepared in advance by the manufacturer of the fan-out check device. An example of the parameters described in the parameter file 3 is shown in FIG. 3 and the processing 14 will be described. The operating frequency A, the operating voltage E and the operating temperature I obtained in 13 and the parameter file 3 corresponding to the operating environment are illuminated. In total, the corresponding parameters are a, e, and i, respectively, and are obtained. In some cases, conversion is performed here to calculate parameters.

In a process 15, an output unit drive capability value is calculated from the output unit drive capability standard value obtained in step 12 and the parameters obtained in step 14.

Under the condition 16, the total net capacity calculated in step 11 is compared with the output drive capacity calculated in step 15.

If the capacity of the net is equal to or smaller than the drive capacity of the output unit by the process 17, it is determined to be OK, and the result and the margin value are output to the result file 6.

Otherwise, processing 18 determines that N
It is determined to be G, and the result and the value that has exceeded are output to the result file 7.

Since there are usually a plurality of nets in the logic circuit, it is determined in step 37 whether all the nets have been compared. If all the nets have been compared, the process ends in step 38; otherwise, the process returns to step 34. .

Here, the output unit drive standard value, the user input, and the parameters of the parameter file are required for calculating the drive capability value. However, the parameter file includes three types of operation frequency, operating voltage, and operating temperature. If drive capability values corresponding to each set of parameters are stored in advance, the fan-out check calculation unit refers to the three types of parameters from the parameter file, and then extracts drive capability values corresponding to those parameters from the parameter file. Only the calculation load is reduced. At this time, the output unit drive standard value becomes unnecessary.

[0036]

By performing the fan-out check of the above-mentioned means, all users can set the LSI in any environment.
It is possible to calculate an output drive capacity value that is adapted to the operating environment even if is used, and it is possible to use an element having a scale and drive capacity corresponding to the actual operating environment,
As a result, an effect of reducing the area of the entire LSI is produced.

[Brief description of the drawings]

FIG. 1 is a configuration of a fan-out check in an embodiment.

FIG. 2 is a flowchart showing an operation of a fan-out check calculation unit 5 of FIG.

FIG. 3 is an example of parameters stored in a parameter file 3 corresponding to the LSI operating environment in FIG. 1;

FIG. 4 is an example of a logic circuit in a circuit information file 1;

FIG. 5 is an example of parameters input in an operating environment (user input) 4 of FIG. 1;

FIG. 6 shows a configuration of a conventional fan-out check.

FIG. 7 is a flowchart showing an operation in a fan-out check calculation unit 27 of FIG. 6;

[Explanation of symbols]

1 Circuit information file (net list) 2 Fan-out check information file 3 Parameter file corresponding to LSI operating environment 4 Operating environment (user input) 5 Fan-out check calculator 6 Result file (OK) 7 Result file (NG Case) 8 Start 9 Input circuit information file 10 Obtain input terminal capacity and net capacity of each element from fanout check information file 11 Calculate total capacity of each net 12 Fanout check information file Obtain the output unit drive capability standard value 13 Obtain information on the LSI operating environment from the user 14 Obtain parameters corresponding to the operating environment input by the user from the fanout check information file 15 Calculate the output unit drive capability value of each net 16 Output drive Capacity value ≧ Net capacity 17 Result file (OK) and margin value 18 Result file (NG) and over value 19 All nets compared 20 End 21 Net 22 Output unit connected to net 23 Input unit connected to net A 24 Input unit B connected to the network B 25 Circuit information file 26 Fan-out check information file 27 Fan-out check calculation unit 28 Result file (OK or NG) 29 Start 30 Input circuit information file 31 Fan-out check information file Calculate the input terminal capacitance and net capacitance of each element from the equation 32 Calculate the total capacitance of each net 33 Obtain the output drive standard value of each net from the fan-out check information file 34 Output drive capacity ≧ net capacity 35 Result file (OK) Margin value output 36 result file (NG) and the over value output 37 comparator already 38 finished all nets and

Claims (2)

(57) [Claims] For each net, the drive capacity of an output unit connected to the net is compared with the total capacity of the net.
In the fan-out check function that determines whether the net capacity connected to the net is appropriate,
A fan having a function of calculating a drive capacity based on three data: parameter data corresponding to an operation environment prepared in advance by a manufacturer, drive unit reference value data, and operation environment data input by a user. Out-check device. 2. A circuit information file storing a logic circuit diagram of a semiconductor integrated circuit, a fan-out check information file storing an input capacity and a net capacity of each logic element which is a component of the semiconductor integrated circuit, A fan-out check device having a fan-out check calculating unit, further comprising a parameter file provided in advance corresponding to an operating environment of the semiconductor integrated circuit, wherein the fan-out check calculating unit is configured to receive information input from outside. From the parameter file based on the selected parameter,
A fan-out check device, wherein a driving capability value of each of the logic elements is obtained using the parameter.