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/************************************************
/************************************************
The Verilog HDL code example is from the book
The Verilog HDL code example is from the book
Computer Principles and Design in Verilog HDL
Computer Principles and Design in Verilog HDL
by Yamin Li, published by A JOHN WILEY & SONS
by Yamin Li, published by A JOHN WILEY & SONS
************************************************/
************************************************/
module div_restoring (a,b,start,clk,clrn,q,r,busy,ready,count);
module div_nonrestoring (a,b,start,clk,clrn,q,r,busy,ready,count);
input [31:0] a; // dividend
input [31:0] a; // dividend
input [15:0] b; // divisor
input [15:0] b; // divisor
input start; // start
input start; // start
input clk, clrn; // clk,reset
input clk, clrn; // clk,reset
output [31:0] q; // quotient
output [31:0] q; // quotient
output [15:0] r; // remainder
output [15:0] r; // remainder
output reg busy; // busy
output reg busy; // busy
output reg ready; // ready
output reg ready; // ready
output [4:0] count; // counter
output [4:0] count; // count
reg [31:0] reg_q;
reg [31:0] reg_q;
reg [15:0] reg_r;
reg [15:0] reg_r;
reg [15:0] reg_b;
reg [15:0] reg_b;
reg [4:0] count;
reg [4:0] count;
wire [16:0] sub_out = {reg_r,reg_q[31]} - {1'b0,reg_b}; // sub
wire [16:0] sub_add = reg_r[15]?
wire [15:0] mux_out = sub_out[16]? // restoring
{reg_r,reg_q[31]} + {1'b0,reg_b} : // + b
{reg_r[14:0],reg_q[31]} : sub_out[15:0]; // or not
{reg_r,reg_q[31]} - {1'b0,reg_b}; // - b
assign q = reg_q;
assign q = reg_q;
assign r = reg_r;
assign r = reg_r[15]? reg_r + reg_b : reg_r; // adjust r
always @ (posedge clk or negedge clrn) begin
always @ (posedge clk or negedge clrn) begin
if (!clrn) begin
if (!clrn) begin
busy <= 0;
busy <= 0;
ready <= 0;
ready <= 0;
end else begin
end else begin
if (start) begin
if (start) begin
reg_q <= a; // load a
reg_q <= a; // load a
reg_b <= b; // load b
reg_b <= b; // load b
reg_r <= 0;
reg_r <= 0;
busy <= 1;
busy <= 1;
ready <= 0;
ready <= 0;
count <= 0;
count <= 0;
end else if (busy) begin
end else if (busy) begin
reg_q <= {reg_q[30:0],~sub_out[16]}; // << 1
reg_q <= {reg_q[30:0],~sub_add[16]}; // << 1
reg_r <= mux_out;
reg_r <= sub_add[15:0];
count <= count + 5'b1; // counter++
count <= count + 5'b1; // count++
if (count == 5'h1f) begin // finished
if (count == 5'h1f) begin // finish
busy <= 0;
busy <= 0;
ready <= 1; // q,r ready
ready <= 1; // q,r ready
end
end
end
end
end
end
end
end
endmodule
endmodule