Assignment Extension Past 32-Bits - 2023.1 English

Vivado Design Suite User Guide: Synthesis (UG901)

Document ID
UG901
Release Date
2023-06-09
Version
2023.1 English

If the expression on the left-hand side of an assignment is wider than the expression on the right-hand side, the left-hand side is padded to the left according to the following rules:

  • If the right-hand expression is signed, the left-hand expression is padded with the sign bit.
  • If the right-hand expression is unsigned, the left-hand expression is padded with 0 (zero).
  • For unsized x or z constants only, the following rule applies:

If the value of the right-hand expression's leftmost bit is z (high impedance) or x (unknown), regardless of whether the right-hand expression is signed or unsigned, the left-hand expression is padded with that value (z or x, respectively).