one-hot to binary

[Michael]

Hello,

Does anyone know some optimal Verilog generic function for
convertion one-hot number into binary?
For example,
4'b0001 -> 1
4'b0010 -> 2
4'b0100 -> 3
4'b1000 -> 4
etc

Thanks in advance,
Michael

[vittal]

Hi,
I think the problem is same as searching for a '1' in the string.
so u can check out any search method.there are a lot of them
like binary search,linear search etc...
Vits

Post by Michael
Hello,
Does anyone know some optimal Verilog generic function for
convertion one-hot number into binary?
For example,
4'b0001 -> 1
4'b0010 -> 2
4'b0100 -> 3
4'b1000 -> 4
etc
Thanks in advance,
Michael

[Michael]

There is one stric condition: there is ony ONE '1' there.
I believe there are good implementations exist.

Post by vittal
Hi,
I think the problem is same as searching for a '1' in the string.
so u can check out any search method.there are a lot of them
like binary search,linear search etc...
Vits

Post by Michael
Hello,
Does anyone know some optimal Verilog generic function for
convertion one-hot number into binary?
For example,
4'b0001 -> 1
4'b0010 -> 2
4'b0100 -> 3
4'b1000 -> 4
etc
Thanks in advance,
Michael

[Alex]

Works on up to 32 bit numbers:


function integer convert;
input grey_num;
integer grey_num,i;
for (i=0; i<32; i=i+1) if (grey_num[i]) convert = i+1;
endfunction


-Alex

Post by Michael
Hello,
Does anyone know some optimal Verilog generic function for
convertion one-hot number into binary?
For example,
4'b0001 -> 1
4'b0010 -> 2
4'b0100 -> 3
4'b1000 -> 4
etc
Thanks in advance,
Michael

[Michael]

It looks like a big mux. You don't reck the number has ONLY ONE '1'.

Post by Alex
function integer convert;
input grey_num;
integer grey_num,i;
for (i=0; i<32; i=i+1) if (grey_num[i]) convert = i+1;
endfunction
-Alex

Post by Michael
Hello,
Does anyone know some optimal Verilog generic function for
convertion one-hot number into binary?
For example,
4'b0001 -> 1
4'b0010 -> 2
4'b0100 -> 3
4'b1000 -> 4
etc
Thanks in advance,
Michael

[Alex]

Then, add agrument check to function:

function integer convert;
input grey_num;
integer grey_num,i, sum;
begin
sum = 0;
for (i=0; i<32; i=i+1) begin
sum = sum + grey_num[i];
if (sum > 1) $display("<%m> ERROR: %b is not grey code", grey_num);
if (grey_num[i]) convert = i+1;
end
end
endfunction

Note, you still don't have to bother with parameters.

-Alex

Post by Michael
It looks like a big mux. You don't reck the number has ONLY ONE '1'.

Post by Alex
function integer convert;
input grey_num;
integer grey_num,i;
for (i=0; i<32; i=i+1) if (grey_num[i]) convert = i+1;
endfunction
-Alex

Post by Michael
Hello,
Does anyone know some optimal Verilog generic function for
convertion one-hot number into binary?
For example,
4'b0001 -> 1
4'b0010 -> 2
4'b0100 -> 3
4'b1000 -> 4
etc
Thanks in advance,
Michael

[Jonathan Bromley]

Post by Michael
Does anyone know some optimal Verilog generic function for
convertion one-hot number into binary?
For example,
4'b0001 -> 1
4'b0010 -> 2
4'b0100 -> 3
4'b1000 -> 4

Elsewhere you've already said that you can guarantee that there
is only one bit set in the input word. In that case, the following
works well:

module onehot_to_binary
#(parameter output_bits=3, input_bits=1<<output_bits)
( input wire onehot[input_bits-1:0],
output reg binary[output_bits-1:0]);

always @onehot begin : converter
integer i;
reg result [output_bits-1:0];
result = 0;
for (i=0; i<input_bits; i=i+1)
if (onehot[i]) result = result | i;
binary = result;
end

endmodule

Of course it will give crazy results if you have more than one bit
set in the input "onehot" vector.
--
Jonathan Bromley, Consultant

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