Verilog generate constructs are evaluated at elaboration, which occurs after parsing the HDL (and preprocessor), but before simulation begins. 9,833. 2 Answers. #if checks symbol's value. Parameters are typically used to specify the width of variables and time delays. In this article. I have set the PARAM_1 & PARAM_2 to ZERO from the project settings, as suggested on this discussion. Conditional compilation can be achieved with Verilog `ifdef and `ifndef keywords. Instead of using a `define statement, you can define the Verilog macro with a Quartus setting in the .qsf file. Otherwise, I would have to do the following: #ifdef GCC some code #else if ALPHA same code as GCC Thanks in advance, dedham_ma_man 04-21-2006 #2. Identifiers can be defined by a #define directive or on the command line. The #ifdef identifier statement is . Verilog compiler directives: `define, `default_nettype, `ifdef, `ifndef, `else, `endif, `undef, `include, `resetall, `timescale. Any code that is not compiled must still be valid Verilog code. This conditional statement is used to make a decision on whether the statements within the if block should be executed or not. P.S. November 12, 2013 at 9:45 pm. The expression #ifdef Name evaluates to true in Name has been #define d. In this case (true), the input file lines are processed until a #elseif, #else, or #endif directive is encountered. Not sure if there's a better way (and I've not checked that even this will work), but one way could be to create a file, defines.v with: i.e. "System Verilog Macro" is one of the many solutions to address such duplication. I'm not sure if that is the case in Verilog, but I do know anything in an ifdef is not evaluated if the condition is not met (acts more like #include) - so you can stick code in there that may or may not compile. Read the documentation on 'make'. After it is defined, is referenced using the macro name with a preceding ` (back-tic) character. After it is defined, is referenced using the macro name with a preceding ` (back-tic) character. Multiple files may be given on the sames line, or various files may be read in subsequent lines. In Verilog-XL, `define can interact with the `ifdef tree in subtle ways. #ifdef identifier #ifndef identifier. The #ifdef identifier statement is . In fact, the SV standard says that each file should be a unique compilation unit by default.or at least, each file compiled separately on the command line. For instance, Verilog-XL accepts the following input: `define condition 1 `define myendif `endif `ifdef condition assign w1 = 1 ; `myendif. OR condition in #ifdef. read -formal will also define the FORMAL macro, which can be used to separate a section having formal properties from the . If you define in a module, it still stays declared after the module. You can use the #ifdef and #ifndef directives anywhere #if can be used. if-else-if This conditional statement is used to make a decision about whether certain statements should be executed or not `include includes the contents of another Verilog source file. While this is not wrong, I don't like leaving it there that simplistic. However, it seems SV only support directives like `ifdef, but no `if, so I have no idea on how to do conditional compile according to the value of the macro. `ifdef, `ifndef, `elsif, `else and `endif conditionally compiles Verilog code, depending on whether or not a specified macro is defined. . These keywords can appear anywhere in the design and can be nested one inside the other. Salem. #ifdef and macro expansion is a simple text-replacement, made by a preprocessor before the compiler sees the code. Moreover, one can use an optional generate block to test the value of macro/parameters. The`ifdef,`else,`elsif, and`endif compiler directives work together in the following manner: — When an `ifdef is encountered, the ifdeftext macro identifier is tested to see if it is defined as a text macro name using `demobile within the Verilog HDL source description, The #ifdef, #ifndef , #elseif, #elif, #else, and #endif are the logical . The Verification Community is eager to answer your UVM, SystemVerilog and Coverage related questions. This makes it extremely versatile, at the cost of having no language knowledge at all. In Verilog, there are various compiler directives to set the timescale of simulation, control the compiler flow. Conditional Compilation (#if, #ifdef, #ifndef, #else, #elif, #endif, and defined) Six directives are available to control conditional compilation. The`ifdef,`else,`elsif, and`endif compiler directives work together in the following manner: — When an `ifdef is encountered, the ifdeftext macro identifier is tested to see if it is defined as a text macro name using `define within the Verilog HDL source description. verilog parameter module Note that the Verilog generate statement was added with the Verilog 2001 standard and is not supported by all tools. Its the conditional compilation directive that is used to include either optional or alternative lines of Verilog HDL source description during compilation. If the text_macro_name is defined, then the lines following the `ifdef directive are included. Otherwise assign some other signal. is there an equivalent in VHDL? `endif to check whether the macro is defined or not. Therefore, #ifdef is not limited to processing and generating legal syntax. I have verilog like 'ifdef PARAM_1. Using the GUI to define the 'ifdef doesn't help. kpkrishna. A parameter is a constant that is local to a module that can optionally be redefined on an instance. Parameters are typically used to specify the width of variables and time delays. These keywords can appear anywhere in the design and can be nested one inside the other. Verilog-A provides a familiar set of language preprocessing directives for macro definitions, conditional compilation of code, and file inclusion. Conditional Compilation directive switches vs Simulation directive switches Verilog has following conditional compiler directives. module foo(. Full Access. `ifdef A `define AorB `elsif B `define AorB `endif `idfef AorB . #ifdef checks whether a single identifier with the given name exists, that's right. The #ifdef and #ifndef preprocessor directives have the same effect as the #if directive when it's used with the defined operator.. Syntax. Parameters must be defined within module boundaries using the keyword parameter. : #ifdef is simply the short form of #if defined, however, does not support complex condition. `endif You would nest the `ifdef to define AandB — Dave Rich, Verification Architect, Siemens EDA. They may not be portable and may not invoke the same actions. A compiler directive may be used to control the compilation of a Verilog description. You can remove the `else/else conditions as per your requirement. 5 mins. Yes, it is called the conditional compile construct `ifdef or `ifndef. #ifdef or #ifndef checks symbol's existence. You could even use the C preprocessor to do #ifdef . Macros can be used to improve the readability and maintainability of the Verilog code. You can treat a define no existing as the default value of a generic (say 0) and take a different action if the generic has a different value. Verilog has a set of control flow blocks and mechanisms to achieve the same. It is mostly identical to #if defined . You can control the value of the Verilog macro using a script. `ifdef FLASH_IS_1MB `define FLASH_TEA 19000000000 //19s max for 1MB erase cycle `elsif FLASH_IS_512KB `define FLASH_TEA 12000000000 //12s max for 512KB erase cycle `elsif FLASH_IS_256KB `define FLASH_TEA 6000000000 //6s max for 256KB erase cycle `elsif FLASH_IS_128KB `define FLASH_TEA 4000000000 //4s max for 128KB erase cycle `endif Conditional generate constructs select at most one block of code between multiple blocks. Some Verilog designs use a `define statement, possibly located inside a file referenced by an `include statement, to control something managed with `ifdef or `ifndef. It can exist either inside or outside of a module declaration, and. These directives can be nested. They delimit blocks of program text that are compiled only if a specified condition is true. Parameters must be defined within module boundaries using the keyword parameter. Hardware behavior cannot be implemented without conditional statements and other ways to control the flow of logic. Conditional generate constructs include if-generate and case-generate forms. #if defined (LINUX) || defined (ANDROID) // your code here #endif /* LINUX || ANDROID */. #ifdef identifier #ifndef identifier. Compiler Directives in Verilog. A `define is a global macro. `define the things you want found by the `ifdef. 1,426. We encourage you to take an active role in the Forums by answering and commenting to any questions that you are able to. Such macro is very efficient and can help save a lot of time if used properly in the SV environment. Download chapter PDF. Generate should not be used if your design must be compiled by any unknown tools. In this article. any non-zero value), all statements within that particular if block will be executed Full . The keyword `ifdef simply tells the compiler to include the piece of code until the next `else or `endif if the given macro called FLAG is defined using a `define directive. **BEST SOLUTION** vhdl doesn't have a macro language but it has generics. The simple if—else decision flow, however, can be awkward when there are multiple decisions to make. The `ifdef directive checks that a macro has been defined, and if so, compiles the code that follows. The #ifdef directive has the following syntax: #ifdef identifier newline This directive checks whether the identifier is currently defined. Conditional compilation can be achieved with Verilog `ifdef and `ifndef keywords. `ifdef, `ifndef, `elsif, `else and `endif conditionally compiles Verilog code, depending on whether or not a specified macro is defined. If the expression evaluates to true (i.e. If such identifiers have not been subsequently undefined, they are considered currently defined. Therefore, does anyone know how to create a #ifdef statement that allows such conditions like this? Formal extensions to Verilog. 8.2.3 The #ifndef Directive verilog_preprocessor_set_file ( verilog_preprocessor_context *preproc, char *file) Clears the stack of files being parsed, and sets the current file to the supplied string. Complier directives are common in any programming language which is based on compilers. 22 Sep 2021. NTCONSOLE and EXPANDED). ¶. By default, `define ARM_CM is defined for all Verilog and SystemVerilog design files. INST_ASIC_MEM_2 'else. I'm not %100 positive, but i'm pretty sure that compiler directives (like `define) get handled in a preprocessing step analogous to #define macros in C. if that is the case then the preprocessor is only looking for compiler directives and could care less about the other Verilog language constructs. You could even use the C preprocessor to do #ifdef . `ifdef `else `elsif `endif `ifndef The `ifdef compiler directive checks for the definition of a text_macro_name. I've written the code of the circuit with a module and it compiles . It is of global scope. 1,527. vhdl log2. If `NUM_OF_INS==2, two assertions are compiled, and if If `NUM_OF_INS==1, only one assertion will be compiled. If the macro has not been defined, the compiler compiles the code (if any) following the optional `else directive. If it evaluates to false (zero or 'x' or 'z'), the statements inside if . Niyati. In this case I want the 'else to be executed. These directives control what portions of Verilog source code will be read in by a software tool. the closest tool I'm aware of is the "if generate . 18 posts. 12-01-2011 02:13 PM. Verilog if-else-if This conditional statement is used to make a decision on whether the statements within the if block should be executed or not. I'd be interested to know if it works (I don't have time to try it myself). Compiler directives may appear anywhere in the source . If the macro is not defined and an `else directive exists . Macros can be used to improve the readability and maintainability of the Verilog code. . void. Answer (1 of 4): A 'define' is a macro, which is of global scope If you define in a module, it still stays declared after the module. Parameter. ifndef_directive ifdef . FYI - I am using 2013.4 Vivado. I believe Modelsim switched to this behavior even when compiling pure Verilog designs. A generate block allows to multiply module instances or perform conditional instantiation of any module. It is when the expression is true (non-zero), then the compiler will compile the code between #ENDIF to the code between #ENDIF. It provides the ability for the design to be built based on Verilog parameters. This paper talks about such SV Macro and their syntaxes and also offers a few examples of where it can be used to save time during design verification . verilog_preprocessor_resetall () Handles the encounter of a `resetall directive as described in annex 19.6 of the spec. Remarks. 22 Sep 2021. I have to build a circuit of an arithmetic right shift operator in verilog and include it in a verilog code of a simple computer. ); `ifdef SYNTHESIS // code to be synthesised `else // code not to be synthesized `endif endmodule . Without generate the best way to do conditional instantiation of modules in Verilog is with `ifdef PARAMETER and `endif surrounding the module instantiation and `define . If a condition is met assign the wire to whatever signal you are controlling. The keyword `ifdef simply tells the compiler to include the piece of code until the next `else or `endif if the given macro called FLAG is defined using a `define directive. Any Verilog file may be read using read -formal <file> within the SymbiYosys script section. One can use `ifdef. Verilog-1995 has the conditional compilation directives: 'ifdef, 'else, 'endif, and 'undef. For examples. You can control what code is compiled by choosing whether to define the text macro, either with `define or with +define+. We encourage you to take an active role in the Forums by answering and commenting to any questions that you are able to. The directives are: `define `else `ifdef . It can exist either inside or outside of a module declaration, and both are treated the same… `include includes the contents of another Verilog source file. 5 mins. View Profile View Forum Posts and the hat of int overfl Join Date . `include file_name // include . Because, unluckily, it is not that simple. The `ifdef checks for the definition of a macro. As a side note, `else is a compiler directive so it will not compile if MY_MACRO is defined. I've just learned that in Verilog you can use an `ifdef statement that makes Quartus ignore the following code (until the next`endif) you can define a macro in the qsf file (or through the GUI) to decide which parts of code to ignore. Yet when `foo is used inside of an ifdef'd-away section, it is not expanded These statements are particularly convenient when the same operation or module instance needs to be repeated multiple times or if certain code has to be conditionally included based on given Verilog parameters. A directive is effective from the point at which it is declared to the point at which another directive overrides it, even across file boundaries. The Verification Community is eager to answer your UVM, SystemVerilog and Coverage related questions. Any code that is not compiled must still be valid Verilog code. Therefore, #ifdef is not limited to processing and generating legal syntax. The Verilog-A and Verilog-AMS Preprocessor. The #elseif, #else, and #endif directives are valid only following a #ifdef directive. For conditional code blocks: Conditional code blocks must open (`ifdef, `ifndef) and close (`endif) in the same file. These directives, as the name suggests, direct how the compiler will compile the code. Both above are the same, which one you use simply depends on your taste. 1,527. vhdl log2. Browse other questions tagged system-verilog or ask your own question. Verilog if-else-if. Complier directives are common in any programming language which is based on compilers. The simple if—else decision flow, however, can be awkward when there are multiple decisions to make. 2) #if defined (NTCONSOLE) & defined (EXPANED) I think it can do it. This makes it extremely versatile, at the cost of having no language knowledge at all. These are from the Verilog 2001 Standard. It is used in the code that needs to be debugged. In SystemVerilog, there's a concept of a compilation unit that can break the global scope of `defines. The #ifdef and #ifndef preprocessor directives have the same effect as the #if directive when it's used with the defined operator.. Syntax. Verilog-1995 has the conditional compilation directives: 'ifdef, 'else, 'endif, and 'undef. If it is defined, then the lines following the `ifdef are included. These directives are equivalent to: #if defined identifier #if !defined identifier. These directives, as the name suggests, direct how the compiler will compile the code. I have two conditions for which I need to test in the same #if or #ifdef (e.g. Compiler directives begin with "`" an accent grave, not an apostrophe Some of these would be called preprocessor commands in "C" Compilers may add additional compiler directives. Verilog Compiler Directives. What is the correct format? If the expression evaluates to true (i.e. Compiler Directives in Verilog. verilog conditional compilation ifdef With 'make' you can use conditional compilation to only build the verilog files you want. Directives are preceded by the accent grave ( ` ) character, which should not be confused with a single quote. any non-zero value), all statements within that particular if block will be executed. https://technotip.com/8575/conditional-compilation-in-c-ifdef-else-endif/In this video tutorial lets learn about preprocessor command or directives like #ifd. Verilog Latch in always@(posedge clk) 2015-03-17; 带有 always@(*) 块的 Verilog 生成语句 2015-08-28; RISCV VERILOG HDL 代码 2016-05-01; Verilog 中的并发 Always 块 2017-08-08; verilog 总是 @ 在 uart 中失败 2013-03-26; Verilog if-else 语句 2015-12-10; 类似于 Verilog HDL 的 PHP 功能块 2017-03-22; Verilog if 语句不 . #ifdef and macro expansion is a simple text-replacement, made by a preprocessor before the compiler sees the code. So you can say: $ make n45tt and then have a rule in the makefile that's like n45tt: vlog n45tt.v Or something. You can use the #ifdef and #ifndef directives anywhere #if can be used. These directives are equivalent to: #if defined identifier #if !defined identifier. The grave accent mark, `, denotes a compiler directive. Download chapter PDF. Then specify this file first in the list of Verilog files to import. (I've seen several when I look through eisting code) 1) #if NTCONSOLE && EXPANDED. Remarks. In Verilog, there are various compiler directives to set the timescale of simulation, control the compiler flow. INST_FPGA_MEM. 8.2. These directives control what portions of Verilog source code will be read in by a software tool. Parameter. March 27, 2017 03:19 PM. A parameter is a constant that is local to a module that can optionally be redefined on an instance. INST_ASIC_MEM_1 'elsif. 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And other ways to control the flow of logic which should not be confused with a module and it.... In any programming language which is based on Verilog parameters to use # ifdef //www.edaboard.com/threads/whats-the-equivalent-of-ifdef-in-vhdl.140473/. > C - how to use # ifdef is simply the short form of # if (... Parameters must be defined within module boundaries using the macro name with a single identifier with the given name,. Accent mark, ` define are used together || ANDROID * / evaluated at,! Ifdef or # ifndef checks symbol & # x27 ; ifdef PARAM_1 compiler directive versatile, at cost! This is not compiled must still be valid Verilog code be synthesised ` else directive exists decision... Be compiled by choosing whether to define the FORMAL ifdef or condition verilog, either with define... Local to a module and it compiles must still be valid Verilog.. I don & # x27 ; m aware of is the & # x27 ; t like it... 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