rptr_empty2.v

使用VHDL编程的异步FIFO程序 经调试可运行

module rptr_empty2 (rempty, rptr, aempty_n, rinc, rclk, rrst_n); 
parameter ADDRSIZE = 4; 
output rempty; 
output [ADDRSIZE-1:0] rptr; 
input aempty_n; 
input rinc, rclk, rrst_n; 
reg [ADDRSIZE-1:0] rptr, rbin; 
reg rempty, rempty2; 
wire [ADDRSIZE-1:0] rgnext, rbnext; 
//--------------------------------------------------------------- 
// GRAYSTYLE2 pointer 
//--------------------------------------------------------------- 
always @(posedge rclk or negedge rrst_n) 
if (!rrst_n) begin 
rbin <= 0; 
rptr <= 0; 
end 
else begin 
rbin <= rbnext; 
rptr <= rgnext; 
end 
//--------------------------------------------------------------- 
// increment the binary count if not empty 
//--------------------------------------------------------------- 
assign rbnext = !rempty ? rbin + rinc : rbin; 
assign rgnext = (rbnext>>1) ^ rbnext; // binary-to-gray conversion 
always @(posedge rclk or negedge aempty_n) 
if (!aempty_n) {rempty,rempty2} <= 2'b11; 
else {rempty,rempty2} <= {rempty2,~aempty_n}; 
endmodule