S_idle=0,S_adivr=1,S_adivn=2,S_div=3,S_err=4, L_state=3,L_cnt=4,Max_cnt=L_divn-L_divr; output [L_divn-1:0] quotient,remainder; output ready,error; input [L_divn-1:0] word1;//dividend input [L_divr-1:0] word2;//divisor
input start,clock,reset;//0,start,1,reset reg [L_state-1:0] state,next_state;
reg Load_words,Subtract,Shift_dividend,Shift_divisor; reg [L_divn-1:0] quotient; reg [L_divn:0] dividend; reg [L_divr-1:0] divisor;
reg [L_cnt-1:0] num_Shift_dividend,num_Shift_divisor; reg [L_divr:0] comparison;
wire MSB_divr=divisor[L_divr-1]; wire ready=((state==S_idle)&&reset); wire error=(state==S_err);
wire Max=(num_Shift_dividend==Max_cnt+num_Shift_divisor); wire sign_bit=comparison[L_divr];
assign remainder=(dividend[L_divn-1:L_divn-L_divr])>num_Shift_divisor;/////////
always @(state or dividend or divisor or MSB_divr) case(state)
S_adivr: if(MSB_divr==0)
comparison=dividend[L_divn:L_divn-L_divr]+{1'b1,~(divisor<<1)}+1'b1; else
comparison=dividend[L_divn:L_divn-L_divr]+{1'b1,~divisor[L_divr-1:0]}+1'b1; default:
comparison=dividend[L_divn:L_divn-L_divr]+{1'b1,~divisor[L_divr-1:0]}+1'b1; endcase
always @(posedge clock or negedge reset)
if(!reset) state<=S_idle; else state<=next_state;
always @(state or word1 or word2 or start or comparison or sign_bit or Max)
begin
Load_words=0;Subtract=0;Shift_dividend=0;Shift_divisor=0; case(state)
S_idle: case(!start)
0: next_state=S_idle;
1: if(word2==0) next_state=S_err;
else if(word1) begin next_state=S_adivr;Load_words=1; end else next_state=S_idle; endcase
S_adivr: case(MSB_divr)
0: if(sign_bit==0) begin next_state=S_adivr;Shift_divisor=1; end else if(sign_bit==1) next_state=S_adivn; 1: next_state=S_div; endcase
S_adivn: case({Max,sign_bit})
2'b00: next_state=S_div;
2'b01: begin next_state=S_adivn;Shift_dividend=1; end 2'b10: begin next_state=S_idle;Subtract=1; end 2'b11: next_state=S_idle; endcase
S_div: case({Max,sign_bit})
2'b00: begin next_state=S_div;Subtract=1; end 2'b01: next_state=S_adivn;
2'b10: begin next_state=S_div;Subtract=1; end
2'b11: begin next_state=S_div;Shift_dividend=1; end endcase
default: next_state=S_err; endcase end
always @(posedge clock or negedge reset) begin
if(!reset) begin
divisor<=0; dividend<=0; quotient<=0;
num_Shift_dividend<=0; num_Shift_divisor<=0; end
else if(Load_words==1) begin
dividend<=word1; divisor<=word2;
quotient<=0;
num_Shift_dividend<=0; num_Shift_divisor<=0; end
else if(Shift_divisor) begin
divisor<=divisor<<1;
num_Shift_divisor<=num_Shift_divisor+1; end
else if(Shift_dividend) begin
dividend<=dividend<<1; quotient<=quotient<<1;
num_Shift_dividend<=num_Shift_dividend+1; end
else if(Subtract) begin
dividend[L_divn:L_divn-L_divr]<=comparison; quotient[0]<=1; end end
endmodule
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