wptr_full2.v

使用VHDL编程的异步FIFO程序 经调试可运行

module wptr_full2 (wfull, wptr, afull_n, winc, wclk, wrst_n); 
parameter ADDRSIZE = 4; 
output wfull; 
output [ADDRSIZE-1:0] wptr; 
input afull_n; 
input winc, wclk, wrst_n; 
reg [ADDRSIZE-1:0] wptr, wbin; 
reg wfull, wfull2; 
wire [ADDRSIZE-1:0] wgnext, wbnext; 
//--------------------------------------------------------------- 
// GRAYSTYLE2 pointer 
//--------------------------------------------------------------- 
always @(posedge wclk or negedge wrst_n) 
if (!wrst_n) begin 
wbin <= 0; 
wptr <= 0; 
end 
else begin 
wbin <= wbnext; 
wptr <= wgnext; 
end 
//--------------------------------------------------------------- 
// increment the binary count if not full 
//--------------------------------------------------------------- 
assign wbnext = !wfull ? wbin + winc : wbin; 
assign wgnext = (wbnext>>1) ^ wbnext; // binary-to-gray conversion 
always @(posedge wclk or negedge wrst_n or negedge afull_n) 
if (!wrst_n ) {wfull,wfull2} <= 2'b00; 
else if (!afull_n) {wfull,wfull2} <= 2'b11; 
else {wfull,wfull2} <= {wfull2,~afull_n}; 
endmodule