asynfifo.v

来自「异步FIFO模块： module asynfifo(rst,iclk,oclk」· Verilog 代码 · 共 80 行

module asynfifo(rst,iclk,oclk,din,wren,rden,dout,full,empty);
input 	rst;
input 	iclk;
input 	oclk;
input 	[7:0] din;
input 	wren;
input 	rden;
output  [7:0] dout;
output 	full;
output 	empty;
reg 	[7:0] dout;
reg 	full;
reg 	empty;
reg 	[9:0] wp_bin;
reg 	[9:0] wp_bin_next;
reg 	[9:0] wp_gray;
wire 	[9:0] wp_gray_next;
reg 	[9:0] rp_bin;
reg 	[9:0] rp_bin_next;
reg 	[9:0] rp_gray;
wire 	[9:0] rp_gray_next;
reg 	[7:0] rams[0:1023];
always @(posedge iclk or posedge rst)
begin
	if(rst)	wp_bin <= 10'h0;
	else 	wp_bin <= wp_bin_next;
end
always @(wp_bin or wren or full)
begin
	if(wren&&!full)
	  	wp_bin_next = wp_bin + 1'b1;
	else 	wp_bin_next = wp_bin;
end
assign wp_gray_next = wp_bin_next^{wp_bin_next>>1};
always @(posedge iclk or posedge rst)
begin
	if(rst) wp_gray <= 10'h0;
	else 	wp_gray <= wp_gray_next;
end
always @(posedge oclk or posedge rst)
begin
	if(rst) rp_bin <= 10'h0;
	else 	rp_bin <= rp_bin_next;
end
always @(rp_bin or rden or empty)
begin
	if(rden&&!empty)
	  	rp_bin_next = rp_bin + 1'b1;
	else 	rp_bin_next = rp_bin;
end
assign rp_gray_next = rp_bin_next^{rp_bin_next>>1};
always @(posedge oclk or posedge rst)
begin
	if(rst) rp_gray <= 10'h0;
	else 	rp_gray <= rp_gray_next;
end
always @(posedge iclk)
begin
	if(wren&&!full)  rams[wp_gray] <= din;
end
always @(posedge oclk)
begin
	if(rden&&!empty) dout <= rams[rp_gray];
end
always @(posedge iclk or posedge rst)
begin
	if(rst) full <= 1'b0;
	else 
		if(wp_gray_next==rp_gray&&wren) full <= 1'b1;
		else 	full <= 1'b0;
end
always @(posedge oclk or posedge rst)
begin
	if(rst) empty <= 1'b1;
	else 
		if(rp_gray_next==wp_gray&&rden) empty <= 1'b1;
		else 	empty <= 1'b0;
end
endmodule