Numbers
4Value Logic Values
A scalar logic net can be one of four possible values:
Value 
Description 
0 
Zero, low, or false. 
1 
One, high, or true. 
x 
Unknown or uninitialized. 
z 
Undriven (floating). 
Integers
Simple integers are numbers constructed from digits and possibly underscores. Underscores are ignored in numbers, so 42_839 is equivalent to 42839.
 Examples:
124
+124
124
42_839
Simple integers are signed unsized numbers. A simple integer specification may not contain an x or z.
Except in VerilogA, integer numbers can be explicitly expressed in decimal, hexadecimal, octal, or binary notation. To do so, use s’bn; where s is an optional decimal number that indicates the size of the constant in bits; b is the base format and n is the number in the specified base. The base format is a one or two character code that signifies the following types of numbers:
b
unsigned binary
o
unsigned octal
d
unsigned decimal
h
unsigned hexadecimal
sb
signed binary
so
signed octal
sd
signed decimal
sh
signed hexadecimal
In hexadecimal numbers the letters a
through f
represent the digits 10
through 15. Letters in integer constants can be either lower or upper case.
 Examples:
63
— unsized unsigned decimal number'd63
— unsized unsigned decimal number'h3f
— unsized unsigned hexadecimal number'o77
— unsized unsigned octal number'b11_1111
— unsized unsigned binary number12'h3f
— 12 bit unsigned hexadecimal number5'sd0
— 5 bit signed decimal number
The letters x
and z
can be given to denote unknown and high impedance
digits in all numbers that use a base format, and _
is ignored. Sized
constants for which the size is larger than the given number are padded on the
left with zeros unless the first digit of the given number is an x
or z
,
which are padded with the x
or z
. The number is truncated on the left if
the size is smaller than the given number.
 Examples:
64'o0
— a 64 bit octal 0 (zero padded)8'hx
— equivalent to8'bxxxx_xxxx
(x
padded)12'hfx
— equivalent to12'b0000_1111_xxxx
(zero padded)8'hfffx
— equivalent to8'b1111_xxxx
(truncated)
Real Numbers
Real numbers must either include a decimal point or a scale factor. If a decimal point is present, there must be digits on both sides. So .12, 9., 4.eE3, and .2e7 are not valid numbers. Underscores are ignored in real numbers. Scale factors are given in the table below. These scale factors are available in VerilogA and VerilogAMS, but not in Verilog.
 Examples:
3.14
0.1
1.2E12
1.30e2
236.123_763e12
1.3u
5.46K
Multiplier 
Name 
Symbol 
10^{12} 
tera 

10^{9} 
giga 

10^{6} 
mega 

10^{3} 
kilo 

10^{3} 
milli 

10^{6} 
micro 

10^{9} 
nano 

10^{12} 
pico 

10^{15} 
fempto 

10^{18} 
atto 

10^{d} 
exponent 

constants.vams
Predefined numbers in the form of compiler directives are included in the file constants.vams and listed in the table below (only available in VerilogA and VerilogAMS). The would be included with:
`include "constants.vams"
Mathematical constants are denoted with a `M_ prefix.

π 
3.14159265358979323846 

2π 
6.28318530717958647693 

π/2 
1.57079632679489661923 

π/4 
0.78539816339744830962 

1/π 
0.31830988618379067154 

2/π 
0.63661977236758134308 

2/√π 
1.12837916709551257390 

e 
2.7182818284590452354 

log_{2} e 
1.4426950408889634074 

log_{10} e 
0.43429448190325182765 

log_{e} 2 
0.69314718055994530942 

log_{e} 10 
2.30258509299404568402 

√2 
1.41421356237309504880 

1/√2 
0.70710678118654752440 
Physical constants use the `P_ prefix.

charge of an electron 
1.602176462 × 10 ^{19} C 

speed of light 
2.99792458 × 10 ^{8} m/s 

Boltzmann’s constant 
1.3806503 × 10 ^{23} J/K 

Planck’s constant 
6.626076 × 10 ^{34} Js 

permittivity of a vacuum 
8.854187817 × 10 ^{12} F/m 

permeability of a vacuum 
4π10 ^{7} H/m 

0 Celsius 
273.15 K 