Two Other Forms of Case Statements

• casez

  • Treats all ‘z’ values in the case conditions as don’t cares, instead of logic values
  • All ‘z’ values can also be represented by ‘?’

• casex

  • Treats all ‘x’ and ‘z’ values in the case conditions as don’t cares, instead of logic values

casez (encoder)

4’b1??? : high_lvl = 3;

4’b01?? : high_lvl = 2;

4’b001? : high_lvl = 1;

4’b0001 : high_lvl = 0;

default : high_lvl = 0;

endcase

• if encoder = 4’b1zzz, then high_lvl = 3

casex (encoder)

4’b1xxx : high_lvl = 3;

4’b01xx : high_lvl = 2;

4’b001x : high_lvl = 1;

4’b0001 : high_lvl = 0;

default : high_lvl = 0;

endcase

• if encoder = 4’b1xzx, then high_lvl = 3

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