[sv-bc] query on evaluation of typecast expression

Hi,


  1.  Consider the scenario,
       module test(output reg [7:0] out1);
       reg [3:0]in1,in2;
       typedef reg[7:0] myreg;
       always @(*)
       begin
       in2 = 4'b0101 ;
       in1 = 4'b1100 ;
       out1 = byte'(in2 -in1);
       end
      endmodule
      According to my understanding the  value of out1 will be  00001001 .

   2.  Consider another scenario,
       module test(output reg [7:0] out1);
       reg signed [3:0]in1,in2;
       typedef reg[7:0] myreg;
       always @(*)
       begin
       in2 = 4'b0101 ;
       in1 = 4'b1100 ;
       out1 = byte'(in2 -in1);
       end
      endmodule
      According to my understanding the  value of out1 will be  11111001 
.     
 
  3. Consider another scenario,
       module test(output reg [7:0] out1);
       reg signed [3:0]in1,in2;
       typedef reg[7:0] myreg;
       always @(*)
       begin
       in2 = 4'b0101 ;
       in1 = 4'b1100 ;
       out1 = myreg'(in2 -in1);
       end
      endmodule
      According to my understanding the  value of out1 will be  11111001 
.          
 
4.  Consider another scenario,
       module test(output reg [7:0] out1);
       reg [3:0]in1,in2;
       typedef reg[7:0] myreg;
       always @(*)
       begin
       in2 = 4'b0101 ;
       in1 = 4'b1100 ;
       out1 = myreg'(in2 -in1);
       end
       endmodule
       According to my understanding the  value of out1 will be  00001001 .

     Stanadard simulator behaviour is conflictiing and confusing for the 
above cases.
     Can anyone help me to find out the correct result for the above 
scenarios.
     Your response is important for me.

Thanks & Regards,
Sumay



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