Several Features of VHDL
- VHDL is not case sensitive.
Dout <= A and B; --is the same as doUt <= a AnD b;
- VHDL is not sensitive to spaces and tabs.
nQ <= In_a or In_b; --is the same as nQ < = In_a or In_b;
- Comments in VHDL begin with “–”
--A comment --Another comment PS_reg <= NS_reg; --Here we assign next_state value to present_state
- VHDL statement is terminated with a semicolon.
ifstatement is corresponding with
ifstatement is terminated with
The if-else statement in VHDL is
casestatement is terminated with
loopstatement is terminated with
- Identifiers can only contain letters, digits and underscore character“-”.
- Identifiers must start with an alphabetic character.
- Identifiers must not end with an underscore, and must nerver have two consecutive underscores.
Reserved words cannot be used as identifiers. Some common reserved words are listed below.
access after alias all attribute block body buffer bus constant exit file for function generic group in is label loop mod new next null of on open out range rem return signal shared then to type until use variable wait while with