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61 lines
2.0 KiB
Systemverilog
Executable File
61 lines
2.0 KiB
Systemverilog
Executable File
//------------------------------------------------------------------------------
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// clogb2.svh
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// published as part of https://github.com/pConst/basic_verilog
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// Konstantin Pavlov, pavlovconst@gmail.com
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//------------------------------------------------------------------------------
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// INFO ------------------------------------------------------------------------
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// Calculates counter width based on specified vector/RAM depth
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// see also: http://www.sunburst-design.com/papers/CummingsHDLCON2001_Verilog2001.pdf
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//
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// WARNING:
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// ========
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// - clogb2() usage is a quite obsolete technique, left from Verilog-2001 era
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// when system function $clog2() was not supported or was implemented falcely
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//
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// - don`t use clogb2() for new designs! Instead:
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//
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// - use $clog2(DEPTH) when declaring wr_addr[] pointer, which can refer any
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// RAM element from 0 to DEPTH-1
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//
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// - use $clog2(DEPTH+1) to declare counters, which should hold any walue from
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// 0 up to the DEPTH (inclusive)
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//
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//
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// Compared with system function $clog2():
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// =======================================
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// $clog2(0) = 0; clogb2(0) = 0;
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// $clog2(1) = 0; clogb2(1) = 1;
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// $clog2(2) = 1; clogb2(2) = 2;
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// $clog2(3) = 2; clogb2(3) = 2;
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// $clog2(4) = 2; clogb2(4) = 3;
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// $clog2(5) = 3; clogb2(5) = 3;
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// $clog2(6) = 3; clogb2(6) = 3;
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// $clog2(7) = 3; clogb2(7) = 3;
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// $clog2(8) = 3; clogb2(8) = 4;
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// $clog2(9) = 4; clogb2(9) = 4;
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// $clog2(10)= 4; clogb2(10)= 4;
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// $clog2(11)= 4; clogb2(11)= 4;
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// $clog2(12)= 4; clogb2(12)= 4;
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// $clog2(13)= 4; clogb2(13)= 4;
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// $clog2(14)= 4; clogb2(14)= 4;
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// $clog2(15)= 4; clogb2(15)= 4;
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// $clog2(16)= 4; clogb2(16)= 5;
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//
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// Function should be instantiated inside a module
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// But you are free to call it from anywhere by its hierarchical name
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//
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// To add clogb2 function to your module:
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// `include "clogb2.svh"
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//
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function integer clogb2;
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input [31:0] depth;
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for( clogb2=0; depth>0; clogb2=clogb2+1 ) begin
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depth = depth >> 1;
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end
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endfunction
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