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/////////////////////////////////////////////////////////////////////
//// ////
//// Non-restoring unsigned divider ////
//// ////
//// Author: Richard Herveille ////
//// richard@asics.ws ////
//// www.asics.ws ////
//// ////
/////////////////////////////////////////////////////////////////////
//// ////
//// Copyright (C) 2002 Richard Herveille ////
//// richard@asics.ws ////
//// ////
//// This source file may be used and distributed without ////
//// restriction provided that this copyright statement is not ////
//// removed from the file and that any derivative work contains ////
//// the original copyright notice and the associated disclaimer.////
//// ////
//// THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY ////
//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED ////
//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS ////
//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR ////
//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, ////
//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES ////
//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE ////
//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR ////
//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF ////
//// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ////
//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT ////
//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE ////
//// POSSIBILITY OF SUCH DAMAGE. ////
//// ////
/////////////////////////////////////////////////////////////////////
`timescale 1 ns / 1 ns
module div_signed(clock, clken, numer, denom, quotient, remain);
//
// parameters
//
parameter stages = 32; // controls # of pipeline stages
localparam width = stages;
parameter z_width = 2*width; // internally used width
parameter width_n = width; // width of numerator and quotient <= width
parameter width_d = width; // width of denominator and remainder <= width
//
// inputs & outputs
//
input clock; // system clock
input clken; // clock enable
input [width_n -1:0] numer; // dividend
input [width_d -1:0] denom; // divisor
output [width_n -1:0] quotient; // quotient
output [width_d -1:0] remain; // remainder
reg [width_n-1:0] quotient = {(width_n){1'b0}};
reg [width_d-1:0] remain = {(width_d){1'b0}};
//
// functions
//
function [z_width:0] gen_s;
input [z_width:0] si;
input [z_width:0] di;
begin
if(si[z_width])
gen_s = {si[z_width-1:0], 1'b0} + di;
else
gen_s = {si[z_width-1:0], 1'b0} - di;
end
endfunction
function [width-1:0] gen_q;
input [width-1:0] qi;
input [z_width:0] si;
begin
gen_q = {qi[width-2:0], ~si[z_width]};
end
endfunction
function [width-1:0] assign_s;
input [z_width:0] si;
input [z_width:0] di;
reg [z_width:0] tmp;
begin
if(si[z_width])
tmp = si + di;
else
tmp = si;
assign_s = tmp[z_width-1:z_width-width];
end
endfunction
//
// variables
//
reg [width-1:0] q_pipe [width-1:0];
reg [z_width:0] s_pipe [width:0];
reg [z_width:0] d_pipe [width:0];
// added by janders; April 2015
// spipe1 and spipe2 keep track of whether we need to change the sign
// of the quotient and remainder
// inumer, idenom are the numerator and denominator in absolute value
reg [width-1:0] spipe1;
reg [width-1:0] spipe2;
reg [width-1:0] inumer;
reg [width-1:0] idenom;
integer n0, n1, n2;
// This always block takes the absolute value of the numerator
always @(numer)
if (numer[width_n-1])
inumer = ~numer + 1'b1;
else
inumer = numer;
// Take the absolute value of the denominator
always @(denom)
if (denom[width_d-1])
idenom = ~denom + 1'b1;
else
idenom = denom;
// generate divisor (d) pipe
always @(idenom)
begin
d_pipe[0] <= {1'b0, idenom, {(z_width-width){1'b0}} };
end
always @(posedge clock)
if(clken)
for(n0=1; n0 <= width; n0=n0+1)
d_pipe[n0] <= d_pipe[n0-1];
// generate internal remainder pipe
always @(inumer)
begin
s_pipe[0] <= {{(width){1'b0}}, inumer};
end
always @(posedge clock)
if(clken)
for(n1=1; n1 <= width; n1=n1+1)
s_pipe[n1] <= gen_s(s_pipe[n1-1], d_pipe[n1-1]);
// generate quotient pipe
always @(posedge clock)
q_pipe[0] <= 0;
always @(posedge clock)
if(clken)
for(n2=1; n2 < width; n2=n2+1)
q_pipe[n2] <= gen_q(q_pipe[n2-1], s_pipe[n2]);
// This is a little tricky. The spipe1 stores whether the
// remainder's should be made negative. In the LLVM srem instruction
// the remainder takes the sign of the numerator.
// The spipe2 stores whether the quotient is to be made negative.
// This follows the usual math semantics. It should be negative
// if the signs of the dividend and divisor are different (XOR).
// Added by janders; April 2015
integer n,m;
always @(posedge clock)
if(clken)
begin
spipe1[0] <= numer[width-1];
for(n=1; n < width; n=n+1)
spipe1[n] <= spipe1[n-1];
spipe2[0] <= numer[width-1] ^ denom[width-1];
for(m=1; m < width; m=m+1)
spipe2[m] <= spipe2[m-1];
end
always @(posedge clock)
if(clken) // we may need to change the sign of the remainder
remain <= spipe1[width-1] ? ~assign_s(s_pipe[width], d_pipe[width]) + 1'b1 : assign_s(s_pipe[width], d_pipe[width]);
always @(posedge clock)
if(clken) // we may need to change the sign of the quotient
quotient <= spipe2[width-1] ? ~gen_q(q_pipe[width-1], s_pipe[width]) + 1'b1 : gen_q(q_pipe[width-1], s_pipe[width]);
endmodule
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