tailieunhanh - ANALOG BEHAVIORAL MODELING WITH THE VERILOG-A LANGUAGE- P7

ANALOG BEHAVIORAL MODELING WITH THE VERILOG-A LANGUAGE- P7: Verilog-A is a new hardware design language (HDL) for analog circuit and systems design. Since the mid-eighties, Verilog HDL has been used extensively in the design and verification of digital systems. However, there have been no analogous high-level languages available for analog and mixed-signal circuits and systems. | Compiler Directives System Tasks and Functions The character introduces a language construct that enables development of user-defined tasks and functions. A name following the is interpreted as a system task or a system function. See Appendix B. for Verilog-A system tasks and their descriptions Compiler Directives All Verilog-A language compiler directives are preceded by the character. This character is called accent grave. It is different from the character which is the single quote character. The scope of compiler directives extends from the point where it is processed across all files processed to the point where another compiler directive supersedes it or the processing completes. The following compiler directives are available define else endif ifdef include resetall undef define and undef The directive definecreates a macro for text substitution. This directive can be used both inside and outside module definitions. After a text macro is defined it can be used in the source description by using the character followed by the macro name. The compiler substitutes the text of the macro for the string macro_name. Lexical Conventions and Compiler Directives 165 Please purchase PDF Split-Merge on to remove this watermark Lexical Conventions and Compiler Directives All compiler directives are considered predefined macro names it is illegal to redefine a compiler directive as a macro name. A text macro can be defined with arguments. This allows the macro to be customized for each individual use. An example of the definition and use is illustrated below define threshold define pp_max a b a b a b @ cross V thr - threshold V out pp_max V in1 V in2 The macro text can be any arbitrary text specified on the same line as the text macro name. If more than one line is necessary to specify the text the newline must be preceded by a backslash . The first newline not preceded by a backslash will end the macro text The newline preceded by