LEXICAL TOKENS
 

1. White Space - Spaces, Tabs(t), Newlines(n), and Formfeeds.
2. Comments
   1. A one-line comment shall start with the two characters // and end with a new line.
   2. A block comment shall start with /* and end with */.
      1. Block comments shall not be nested.
      2. The one-line comment token // shall not have any special meaning in a block comment.

3. Operators -  Unary, Binary and Ternary
   1. Unary operators shall appear to the left of their operand.
   2. Binary operators shall appear between their operands.
   3. A conditional operator shall have two operator characters that separate three operands.
4. Constants – Integer constants and Real constants
5. Strings - A string is a sequence of characters enclosed by double quotes ("") and contained on a single line
6. Identifiers:

1. An identifier is used to give an object a unique name so it can be referenced.
2. An identifier is either a simple identifier or an escaped identi.er
3. A simple identifier shall be any sequence of letters, digits, dollar signs ($), and underscore characters (_).
4. The first character of a simple identi.er shall not be a digit or $; it can be a letter or an underscore. Identifiers shall be case sensitive.

Example:

shiftreg_a

busa_index

error_condition

merge_ab

_bus3

n$657

5. Escaped identifiers shall start with the backslash character () and end with white space (space, tab, newline).

·  They provide a means of including any of the printable ASCII characters in an identifier (the decimal values 33 through 126, or 21 through 7E in hexadecimal).

· Neither the leading backslash character nor the terminating white space is considered to be part of the identifier. Therefore, an escaped identi.er cpu3 is treated the same as a nonescaped identifier cpu3.

Example:

busa+index

-clock

***error-condition***

net1/net2

{a,b}

a*(b+c)

7. Keywords -  Keywords are predefined nonescaped identi.ers that are used to define the language constructs. A Verilog HDL keyword preceded by an escape character is not interpreted as a keyword.All keywords are defined in lowercase only.