Mixing Array and Scalar Logical Operators - 2023.1 English

Vivado Design Suite User Guide: Synthesis (UG901)

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2023.1 English

Previously in VHDL, both of the operands of the logical operators needed to be the same size.

VHDL-2008 supports using logical operators when one of the operands is an array and one is a scalar. For example, to AND one bit with all the bits of a vector, the following code was needed:

out1(3) <= in1(3) and in2;
out1(2) <= in1(2) and in2;
out1(1) <= in1(1) and in2;
out1(0) <= in1(0) and in2;

This can now be replaced with the following:

out1<= in1 and in2;