Method of distinguishing bidirectional pins

• US 6,847,926 B1
• Filed: 10/19/2000
• Issued: 01/25/2005
• Est. Priority Date: 10/29/1999
• Status: Active Grant

• Current Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Limited (STMicroelectronics NV)
• Inventors: Ballam, Peter
• Primary Examiner(s): Knight, Anthony
• Assistant Examiner(s): BARNES-BULLOCK, CRYSTAL JOY
• Application Number:
  US09/692,297
• Time in Patent Office: 1,559 Days
• Field of Search: 703/3, 703/4, 703/13, 703/14, 716/4, 716/5, 714/33
• US Class Current: 703/14
• CPC Class Codes: G06F 30/33 Design verification, e.g. functional simulation or model checking

Abstract

A method is described for distinguishing between an input or output signal on a bi-directional pin of a model of a hardware circuit. The method includes the steps of for a bi-directional pin of said model applying signals to said pin at a reduced drive strength such that a driven signal on said pin will be superimposed over the applied signal, and comparing the drive strength on the bi-directional pin and responsive to said comparison determining whether the bi-directional pin is an input or output.

Claims

1. A method of distinguishing between an input and output signal on a bi-directional pin of a model of a hardware circuit the steps of:

for a bi-directional pin of said signals to said bi-directional pin at a reduced drive strength such that a driven signal on said bi-directional pin will be superimposed over the applied signal; and

measuring the drive strength of the signal on the bi-directional pin and responsive to said measurement determining whether the bi-directional pin is an input or output.

2. A method as claimed in claim 1, further comprising the step of providing an output to indicate if the bi-directional pin is an input or an output.

3. A method according to claim 1 wherein said model is a digital model.

4. A method according to claim 3 wherein said digital model is a HDL model.

5. A method as claimed in claim 4, wherein the HDL model utilizes the standard HDL values and a strong signal on the bi-directional pin is replaced by a Z in said applying step.

6. A method according to claim 1, wherein any output from said model has a drive strength greater than said reduced drive strength.

7. A computer program comprising program code that, when executed on a computer, perform any of the steps of any of claims 1 to 6.

8. A system for distinguishing between an input and output signal on a bi-directional pin of a model of a hardware circuit, said system comprising:

means for applying signals to a bi-directional pin of said model at a reduced drive strength such that a driven signal on said pin will be super imposed over the applied signal; and

means for measuring the drive strength of the signal on the bi-directional pin and responsive to said measurement determining whether the bi-directional pin is an input or output.

9. A system as claimed in claim 8, wherein said system is a computer system.