Abstract:
A method and system for performing simultaneous tests and avoiding task collisions using a hardware description language includes designating a timeslot for one or more of the simultaneous tests, associating the designated timeslot with one or more of the tasks to be performed in a test, determining if the designated timeslot is available before executing the tasks associated with timeslots and executing the tasks when the designated timeslots become available.

Description:
TECHNICAL FIELD  
         [0001]    The present invention is related in general to hardware description languages (HDLs) and in particular to a method of performing testbench tests in a HDL to avoid task collisions.  
         BACKGROUND INFORMATION  
         [0002]    Hardware description languages (HDLs) are high level languages used to design, test, and document electronic systems. HDLs allow designers to design at various levels of abstraction. There are several HDLs currently in use. Among them are Verilog and VHDL.  
           [0003]    When designing a field programmable gate array (FPGA), an applications specific integrated circuit (ASIC), or other logic device, a simulation environment that includes a “testbench” and the design under test (DUT) must be created. This environment allows tests to be generated to check the functionality of the logic device that has been created in the HDL. In many instances these tests, which are usually written in the same HDL as the DUT, must communicate with the logic device through a common interface such as a microprocessor interface. The logic device may have many internal blocks of unrelated logic, but must interface through the microprocessor interface, which can present a bottleneck. For example, if two tests are run at the same time, both tests may call tasks that attempt to access the microprocessor interface at the same time, which can cause a test bench task collision. If this occurs, the results can be undeterminable. The present invention provides a method to run concurrent tests on a logic device under test and avoid the problem of task collisions, thus resulting in considerable time savings in the HDL design process. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is an illustration of one example of a prior art HDL testbench system.  
         [0005]    [0005]FIG. 2 is an illustration of one example of a system according to the teachings of the present invention. 
     
    
     SUMMARY  
       [0006]    A method for performing simultaneous tests and avoiding task collisions in a hardware description language includes designating a timeslot for a plurality of simultaneous tests, associating the designated timeslot with one or more tasks to be performed, determining if the designated timeslot is available before executing a task and executing the task when the designated timeslot becomes available.  
       DETAILED DESCRIPTION  
       [0007]    In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.  
         [0008]    Many logic designs are created in a high-level HDL such as Verilog or VHDL. Thorough testing of the device is an important part of the design process and involves the performance of many tests, each of which may include a number of individual tasks. These tasks are typically defined once and called multiple times in the performance of one or more tests. For example, Verilog supports tasks that can be defined once, but are called many times to perform a common task, such as a microprocessor read or write. Even though tests are typically performed on a number of separate parts of the DUT, many tests must still be run sequentially to make sure no task collisions occur. Typically, the highest risk of a task collision is at the microprocessor interface. Since several tests might be able to test different parts of the logic device simultaneously, it would make sense to run the tests concurrently so that the time spent during simulation is minimized if task collisions could be avoided. FIG. 1 shows an example of how the problem of task collisions in an HDL testbench environment have been handled in the past. Step  101  defines the various tests in the HDL testbench. In steps  103 ,  105  and  107  the tests are run sequentially, i.e., at a different time to ensure that task collisions are avoided.  
         [0009]    The method of the present invention enables multiple HDL tests to be run simultaneously. To avoid the possibility of a task collision, the present invention enables each task to be performed and completed before other, potentially conflicting, tasks are allowed to perform.  
         [0010]    To implement the invention of the present application, one must determine how many clock cycles the tasks in question will take to complete and how many tests will be performed at the same time. Once this has been determined, unique timeslots can be assigned to one or more of the tests to be performed simultaneously such that each timeslot will allow for tasks of a test to be completed during the designated timeslot. In this way, advantageously, a number of tests can be performed at the same time, and result in considerable time savings in an HDL verification process.  
         [0011]    [0011]FIG. 2 illustrates a method of running simultaneous HDL tests according to the present invention. Step  201  defines the various tests to be performed in the top level of the testbench and assigns a timeslot to each test. Each task may be evaluated to determine whether it may collide with a task of another test. If the task may potentially collide with any other task, the task is put in the timeslot corresponding to the timeslot assigned to the test to which it belongs. Thus, the task should be defined to include a discrete timeslot symbol or input variable to let it know which timeslot it is to use. The number of bits of the input variable will depend on the number of timeslots required. If the task is certain not to collide with any other task a timeslot is not necessary and may be skipped for that task. After determining the number of clock cycles needed to perform the longest task, timeslots are created by generating a counter in step  202  in the top level test bench of the HDL. For simplicity, a single counter is used to count both timeslots and time. The number of bits in the counter should be sufficient to allow enough time for the longest task of any of the tests to be completed and also to count the number of timeslots needed for the tests to be performed simultaneously. For example, if the longest task takes  10  clock cycles to be performed, and there will be two timeslots, the counter should have at least 5 bits. As many tests as there are timeslots available can be run simultaneously. If more tests are to be run simultaneously additional bits can be added to the counter. For example, to allow for up to 8 timeslots, and a timeslot of up to 16 clock cycles, the counter should have at least 7 bits. In this case, the bottom least significant 4 bits may be used to provide the time to make sure the task can be completed in the up to 16 clock cycles and the top most significant 3 bits at step  204  will allow for 8 different timeslots. These can be used to make sure that the tests  206 ,  212  and  214  running concurrently will not have task collisions.  
         [0012]    When a task is called, the assigned timeslot must be passed to it. At step  206 , test  1 , which has been assigned timeslot  1 , is called. The process checks at step  208  to see if timeslot  1  is indeed available. If it is not, test  1  waits at step  208  until the timeslot is available. Once timeslot  1  becomes available, the task executes at  210 . If another task is to be executed as a part of test  1 , the process again checks to see if timeslot  1  is available. If the assigned timeslot is not yet available, the process again waits for timeslot  1 . When timeslot  1  is available, the additional task is executed at step  213 . The process continues in the same manner until all of the tasks of the test have been completed. In this way, during testing, if the verification process calls another task that might cause a task collision, the task will wait for its designated timeslot. In this example, the passed-in variable timeslot for each task will wait until it matches the top 3 bits in the counter, which is the counter at the top-level test bench. The same procedure applies for tests  2  to test N. Test  2  begins at step  212  and waits for timeslot  2  to become available at  209 . When timeslot  2  is available, the task executes at step  215 . Likewise, test N begins at step  214  and waits for timeslot N to become available at  217 . When timeslot N is available, the task executes at  219 . In this way each test can proceed simultaneously and tasks can be executed in assigned timeslots and will not collide with tasks called from any other tests.  
         [0013]    Not all tasks, of course, will run the risk of a task collision. If any one or more of the tasks for a test would not conflict with tasks to be performed by another simultaneous test there is no need to assign the task a timeslot. In that case, the task will execute without going through the step of determining if a timeslot is available.  
       CONCLUSION  
       [0014]    Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.