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8-to-3 priority encoder code displays two warnings

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usman

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warning message

AOA! i wrote code(given below) for 8-to-3 priority encoder but when i synthesized it on xilinx6.3i, it synthesized but with the following two warning messages

1. WARNING:SpeedCalc:42 - Cannot find referenced model "bel_d_min_period". This generally indicates that there is an inconsistency between versions of the
speed and device data files. Please check to ensure that the XILINX
environment variable is set correctly, if the MYXILINX variable is set, make
sure that it is pointing to patch files that are compatable with the version
of software that the XILINX variable points to.
////////////////////////////////////////////////////////////////
//8-to-3 priority encoder,,,
//priority in descending order,,,in7>in6>.....in0
/////////////////////////////////////////////////
module priorityenc( in,
out,
ld);
input [7:0] in;
output reg [2:0] out;
output ld;

//reg [2:0] out;
assign ld=1;

always @(in)
if (in[7]==1)
out = 3'b111;
else if (in[6]==1)
out = 3'b110;
else if (in[5]==1)
out = 3'b101;
else if (in[4]==1)
out = 3'b100;
else if (in[3]==1)
out = 3'b011;
else if (in[2]==1)
out = 3'b010;
else if (in[1]==1)
out = 3'b001;
else if (in[0]==1)
out=3'b0;
else out=3'b000;
endmodule

2. WARNING:Xst:647 - Input <in<0>> is never used.

Interestingly when in the else portion i assign out value other than 3'b0, then warning 2 disappears

regards,
Muhammad Usman
 

echo47

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warning message

I tried it in ISE 6.3.03i (that's Service Pack 3). I chose part 2v40-4-cs144.

I did not get any SpeedCalc warning. Did you follow the suggestions in your warning message? Maybe your ISE installation got messed up somehow, or maybe you need to install a Service Pack.

The in<0> warning is valid because that bit doesn't affect any module outputs.
 

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