Peter J. Ashenden, in The Designer's Guide to VHDL (Third Edition), 2008. 4.3.4 The Concatenation Operator. The one remaining operator that can be applied to one-dimensional arrays is the concatenation operator (“&”), which joins two array values end to end.For example, when applied to bit vectors, it produces a new bit vector with length equal to the sum of the lengths of the two operands.
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