内建数据类型
四状态：reg, wire, logic, integer, time(默认值为X)
双状态：bit, int, byte, shortint, longint, real(默认值为0)
有符号数：int, byte, shortint, longint, integer(可以使用unsigned申明为无符号数)
🔖 $isunknown操作符:
作用：使用$isunknown操作符，可以在表达式的任意位出现X或Z时返回1
//test_isunknown.sv module test_isunknown(); logic [3:0] din; initial begin din = 4'b1001; //Unknown not found! din = 4'b1x01; //Unknown is detected! din = 4'b1z01; //Unknown is detected! if($isunknown(din)) $display("Unknown is detected!"); else $display("Unknown not found!"); end endmodule
