除法器

`define NUM_STATE_BITS 3

`define IDLE 3'b000

`define COMPUTE1 3'b010

`define COMPUTE2 3'b011

`define COMPUTE3 3'b100

module cl(clk);

parameter TIME_LIMIT = 110000;

output clk;

reg clk;

initial

clk = 0;

always #50 clk = ~clk;

always @(posedge clk)

if ($time > TIME_LIMIT) #70 $stop;

endmodule

module slow_div_system(pb,ready,x,y,r3,sysclk);

input pb,x,y,sysclk;

output ready,r3;

wire pb;

wire [11:0] x,y;

reg ready;

reg [11:0] r1,r2,r3;

reg [`NUM_STATE_BITS-2:0] present_state;

always

begin

@(posedge sysclk) enter_new_state(`IDLE);

r1 <= @(posedge sysclk) x;

r2 <= @(posedge sysclk) 0;

ready = 1;

if (pb)

begin

while (r1 >= y)

begin

@(posedge sysclk) enter_new_state(`COMPUTE1);

r1 <= @(posedge sysclk) r1 - y;

@(posedge sysclk) enter_new_state(`COMPUTE2);

r2 <= @(posedge sysclk) r2 + 1;

@(posedge sysclk) enter_new_state(`COMPUTE3);

r3 <= @(posedge sysclk) r2;

end

end

end

task enter_new_state;

input [`NUM_STATE_BITS-2:0] this_state;

begin

present_state = this_state;

#1 ready=0;

end

endtask

always @(posedge sysclk) #20

$display("%d r1=%d r2=%d r3=%d pb=%b ready=%b", $time, r1, r2, r3,pb,ready);

endmodule

module top;

reg pb;

reg [11:0] x,y;

wire [11:0] quotient;

wire ready;

integer s;

wire sysclk;

cl #20000 clock(sysclk);

slow_div_system slow_div_machine(pb,ready,x,y,quotient,sysclk);

initial

begin

pb= 0;

x = 45;

y = 6;

#250;

@(posedge sysclk);

for (x=45; x<=45; x = x+1)

begin

@(posedge sysclk);

pb = 1;

@(posedge sysclk);

pb = 0;

@(posedge sysclk);

wait(ready);

@(posedge sysclk);

if (x/y === quotient)

$display("ok");

else

$display("error x=%d y=%d x/y=%d quotient=%d",x,y,x/y,quotient);

end

$stop;

end

endendmodule

<執行結果>

Running...
70 r1= x r2= x r3= x pb=0 ready=1
170 r1= 45 r2= 0 r3= 0 pb=0 ready=1
270 r1= 45 r2= 0 r3= 0 pb=0 ready=1
370 r1= 45 r2= 0 r3= 0 pb=1 ready=1
470 r1= 45 r2= 0 r3= 0 pb=0 ready=0
570 r1= 39 r2= 0 r3= 0 pb=0 ready=0
670 r1= 39 r2= 1 r3= 0 pb=0 ready=0
770 r1= 39 r2= 1 r3= 1 pb=0 ready=0
870 r1= 33 r2= 1 r3= 1 pb=0 ready=0
970 r1= 33 r2= 2 r3= 1 pb=0 ready=0
1070 r1= 33 r2= 2 r3= 2 pb=0 ready=0
1170 r1= 27 r2= 2 r3= 2 pb=0 ready=0
1270 r1= 27 r2= 3 r3= 2 pb=0 ready=0
1370 r1= 27 r2= 3 r3= 3 pb=0 ready=0
1470 r1= 21 r2= 3 r3= 3 pb=0 ready=0
1570 r1= 21 r2= 4 r3= 3 pb=0 ready=0
1670 r1= 21 r2= 4 r3= 4 pb=0 ready=0
1770 r1= 15 r2= 4 r3= 4 pb=0 ready=0
1870 r1= 15 r2= 5 r3= 4 pb=0 ready=0
1970 r1= 15 r2= 5 r3= 5 pb=0 ready=0
2070 r1= 9 r2= 5 r3= 5 pb=0 ready=0
2170 r1= 9 r2= 6 r3= 5 pb=0 ready=0
2270 r1= 9 r2= 6 r3= 6 pb=0 ready=0
2370 r1= 3 r2= 6 r3= 6 pb=0 ready=0
2470 r1= 3 r2= 7 r3= 6 pb=0 ready=0
2570 r1= 3 r2= 7 r3= 7 pb=0 ready=1
ok
Stop at simulation time 2650000