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VHDL File Handling in Simulation: Input, Output, and Data Object Management

This guide covers the essentials of using files in VHDL simulations. It explains how to input files into the testbench and output simulation results, emphasizing the structure and types of files as data objects. You’ll learn about the syntax for file type declaration, including examples like `type.integer_file`, and how to manage file operations such as opening and writing. Additionally, we cover key predefined procedures and error handling to ensure your simulations run smoothly. Discover how to effectively manage data types and file contents in your VHDL test environments.

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VHDL File Handling in Simulation: Input, Output, and Data Object Management

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  1. Simulation uses the file as data object: Input a file in test bench for simulation Output a file as the simulation result Print an info(warning, error) during the simulation A VHDL file is a class of object used to store data. Like other object, it must include file-type definition. The file type declaration syntax: Type file_type is file of element_type; Example: Type integer_file is file of integer; Compare with other type declarations: Type state_type is (s0, s1); Subtype sub_integer is integer range 1 to 31

  2. File type declaration --file type that can store ASCII data, readable text. --file type that can store sequence of integers, not readable Signal c_state, n_state: state_type; External file name File operating mode A file declaration creates one (or more) file objects of a given file type. We can declare a file within Architecture, process, package, and subprograms.

  3. optional Predefined procedure OPEN_OK STATUS_ERROR(already opened) NAME_ERROR(file not found) MODE_ERROR(file can’t be opened) Predefined procedure, return values:

  4. Procedure WRITE(file filename: FILE_TYPE; value: in type); It implicitly declared a file type and operation.

  5. Predefined procedure

  6. Write all contents of buf into outfile T h e F i r s t Buf(pointer)

  7. Parameter of the procedure call

  8. Function call and return Boolean value Next; -- only can used in loop, jump to end of loop End loop;

  9. 48 If data bus = 32 bits and control signals = 16 bits, then total test vector needed = 2 to cover all possible test combinations.

  10. TEST Manufacture Test set (ATE, Automatic Test Equipment) VHDL testbench

  11. No semicolon

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