Signed values are not necessarily sign extended because the sign bit is the MSB of the size, not the MSB of the value. If is smaller than value MSB s of value are truncated with warning (tool dependent) If is larger than value MSB s of value are filled Regardless of MSB being 0 or 1, 0 filling is done Left-most Bit Expansion 0 0 extend 1 0 extend x X x or X extend z Z z or Z extendĤ Verilog - Representation of Number Literals(cont.) Some Examples: reg v = 8 b1011 initial $displayb ("v signed =\t", v) //v =, MSBs filled with zeros reg w = 3 b1011 initial $displayb ("w signed =\t", w) //w =, bit 3 truncated then 0 filled //generates Modelsim compile warning (Redundant digits in numeric literal) //Runs without warning or errorĥ Verilog - Representation of Number Literals (cont.) Literal numbers may be declared as signed: 4shf 4 bit number (1111) interpreted as a signed 2s complement value Decimal value is -1. radix Radix of the number b or B : binary o or O : octal h or H : hex d or D : decimal default is decimalĢ Verilog - Representation of Number Literals(cont.) Possible values for value are dependent on the radix Format Prefix Legal characters binary b 01xXzZ? octal o 0-7xXzZ? decimal d 0-9 hexadecimal h 0-9a-fA-FxXzZ? The underscore is a separator used to improve readability e.g.: is easily read as 0x2AE5 The character x or X represents unknown The character z or Z represents high impedance The character? or? same as Z (high impedance) The character? is also don t care to synthesisģ Verilog - Representation of Number Literals(cont.) If prefix is preceded by a number, number defines the bit width If no prefix given, number is assumed to be 32 bits Verilog expands to fill given working from LSB to MSB. A separator, single quote, not a backtick signed Indicates if the value is signed.
Barbossa) Numbers are represented as: value ( indicates optional part) size The number of binary bits the number is comprised of. 1 Verilog - Representation of Number Literals.
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