rptr_empty.v

来自「verilog语言实现」· Verilog 代码 · 共 36 行

module rptr_empty #(parameter ADDRSIZE = 4)
(output reg rempty,
 output [ADDRSIZE-1:0] raddr,
 output reg [ADDRSIZE :0] rptr,
 input [ADDRSIZE :0] rq2_wptr,
 input rinc, rclk, rrst_n);

reg [ADDRSIZE:0] rbin;
wire [ADDRSIZE:0] rgraynext, rbinnext;

//-------------------
// GRAYSTYLE2 pointer
//-------------------
always @(posedge rclk or negedge rrst_n)
if (!rrst_n) 
  {rbin, rptr} <= 0;
else 
  {rbin, rptr} <= {rbinnext, rgraynext};

// Memory read-address pointer (okay to use binary to address memory)
assign raddr = rbin[ADDRSIZE-1:0];
assign rbinnext = rbin + (rinc & ~rempty);
assign rgraynext = (rbinnext>>1) ^ rbinnext;
//---------------------------------------------------------------
// FIFO empty when the next rptr == synchronized wptr or on reset
//---------------------------------------------------------------
assign rempty_val = (rgraynext == rq2_wptr);

always @(posedge rclk or negedge rrst_n)
if (!rrst_n) 
  rempty <= 1'b1;
else 
  rempty <= rempty_val;

endmodule