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[SOLVED] What is the $clog2 built-in function do in systemverilog???

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alam.tauqueer

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Hi All,

Can anyone tell me what is the meaning of $clog2 in SV??

Please tell me the usage also and where I can get the information on it??

I have a expression like

localparam param1 = 2'h2;
localparam param2 = 4'h8;
logic [$clog2(param1*int'(param2))-1:0] out1;

regards,
tauqueer
 

Re: What is the $clog2 built-in function do in systemverilog

According to the standard
The system function $clog2 shall return the ceiling of the log base 2 of the argument (the log rounded up to an integer value). The argument can be an integer or an arbitrary sized vector value. The argument shall be treated as an unsigned value, and an argument value of 0 shall produce a result of 0.
Click to expand...

So $clog2(N) is the number of address bits needed for a memory of size N.

Note that, as pointed out in http://www.eda.org/svdb/view.php?id=2247, it is not "the number of bits needed to express the value" N. Consider the case when N is a power of 2. To calculate that you'd use $clog2(N+1).
 

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