Prev Page Next Page

Std_Logic_1164 Package


Package Std_Logic_1164 is NOT a part of the VHDL Standard Definition. It is defined as IEEE Std 1164.


The Std_Logic_1164 Package contains definitions of types, subtypes, and functions, which extend the VHDL into a multi-value logic. It is not a part of the VHDL Standard, but it is a separate Standard of the same standardization body (Institute of Electrical and Electronics Engineers, IEEE).

Main reason for development and standardization of Std_Logic_1164 was the need for more logical values (than the two defined by the type Bit in the Standard package) with resolution function. The types Std_Logic and Std_Logic_Vector (declared in Std_Logic_1164 package) became de facto industrial standards.


The package contains the following declarations:

See std_logic and std_logic_vector for details.

Important Notes

Prev Page Next Page