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Decimal to binary in verilog3/18/2024 An x or z sets four bits in the hexadecimal base, three bits in the octal base, and one bit in the binary base. These are important for modeling real circuits. X or Z valuesįor representing ‘unknown’ and ‘high impedance,’ Verilog uses x and z. Hence, we prefer sized number specifications. The unsized format will take up 32-bit of memory, which is a total waste in this case. Isn’t it better to write 5'b10101 than 'b10101? As a designer, we always thrive to use our memory allocation efficiently to build efficient hardware. For example: 23456 //32-bit decimal number by default ![]() When no base is specified, it is decimal by default. The default size differs depending on the machine and simulator. Numbers without have a default size of 32 bits. Uppercase legal for number specification Unsized number 2E12 (the exponent symbol can be e or E )Ģ36.Let’s see how we can specify sized numbers in Verilog: 4'b1111 // 4-digit binary numberġ6'hDEF //16-bit haxadecimal number. 4'sd15 // this is equivalent to -(-4~Rd 1), or ~Q0001~R.ĮXAMPLE: Using underscore character in numbersġ. be interpreted as a 2~Rs complement number, held in 8 bits~Wequivalent to -(8~Rd 6)Ĥ'hf // this denotes the 4-bit number ~Q1111~R, to 8'd 6 // this defines the two~Rs complement of 6, Some examples of valid numbers are:Ĥaf // is illegal (hexadecimal format requires ~Rh)ģ'b01x // is a 3-bit number with the leastġ6'hz // is a 16-bit high-impedance numberĮXAMPLE: Using sign with constant numbers The X's mean unknown, and the Z's mean high impedance If no base format is specified the number is assumed to be a decimal number. Numbers consist of strings of digits (0-9, A-F, a-f, x, X, z, Z). Valid base formats are 'b, 'B, 'h, 'H 'd, 'D, 'o, 'O for binary, hexadecimal, decimal, and octal. If no is specified then the default size is at least 32bits and may be larger depending on the machine. The size is always specified as a decimal number. Number : Numbers in verilog are in the following format. You can access any word as m for example but you do not get access to the bits in the word unless you copy the word to another 8-bit reg variable. For example reg m declares m to be a two-dimensional array consisting of 64 eight-bit words. Memory : Verilog allows for two dimensional arrays which typically get used for memory spaces. Here are some typical parameter examples: Parameter declarations are done immediately after the module declaration. For example a 4-bit adder becomes more useful as a design if it is put together as an n-bit adder where n is a parameter specified by the user before compilation. Parameters are used to generalize a design. Parameters : a parameter in Verilog can be any Verilog constant. These are 0 (logic 0), 1 (logic 1), ?, X, or x ( don~Rt care or unknown), and Z or z for high impedance tri-state. ![]() Signal values : signals in Verilog have one of four values. As in C++ variable names should be chosen to assist in documentation. Identifiers may not begin with a digit and may not be the same as a Verilog key word. You can use any letter, digit, the underscore, or $. Identifiers : An identifier is usually a variable. A semicolon is used to indicate the end of a command line and commas are typically used to separate elements in a list. Punctuation : white spaces are ignored in Verilog. Use // for a single line comment or /* */ for a multiline comment. ![]() Comments : Verilog comments are the same as in C++.
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