异步fifo程序没看懂，求指导
module fifo1(rdata, wfull, rempty, wdata, winc, wclk, wrst_n,rinc, rclk, rrst_n);parameter DSIZE = 8; parameter ASIZE = 4;
output rdata;
output wfull;
output rempty;
input wdata;
input winc, wclk, wrst_n;
input rinc, rclk, rrst_n;
reg wfull,rempty;
reg wptr, rptr, wq2_rptr, rq2_wptr, wq1_rptr,rq1_wptr;
reg rbin, wbin;
reg mem; //定义存储器宽度为8，深度为16
wire waddr, raddr; //读写地址
wire rgraynext, rbinnext,wgraynext,wbinnext; //读写的格雷码与二进制码
wire rempty_val,wfull_val;
//-----------------双口RAM存储器--------------------
assign rdata=mem;
always@(posedge wclk)
if (winc && !wfull) mem <= wdata;
//-------------同步rptr 指针-------------------------
always @(posedge wclk or negedge wrst_n)
if (!wrst_n) {wq2_rptr,wq1_rptr} <= 0;
else {wq2_rptr,wq1_rptr} <= {wq1_rptr,rptr}; //这里采用了位拼接操作符
//-------------同步wptr指针---------------------------
always @(posedge rclk or negedge rrst_n)
if (!rrst_n) {rq2_wptr,rq1_wptr} <= 0;
else {rq2_wptr,rq1_wptr} <= {rq1_wptr,wptr}; //
//-------------rempty产生与raddr产生-------------------
always @(posedge rclk or negedge rrst_n) // GRAYSTYLE2 pointer
begin
if (!rrst_n) {rbin, rptr} <= 0;
else {rbin, rptr} <= {rbinnext, rgraynext};
end
// Memory read-address pointer (okay to use binary to address memory)
assign raddr = rbin;
assign rbinnext = rbin + (rinc & ~rempty);
assign rgraynext = (rbinnext>>1) ^ rbinnext; //产生读格雷码
// FIFO empty when the next rptr == synchronized wptr or on reset
assign rempty_val = (rgraynext == rq2_wptr);
always @(posedge rclk or negedge rrst_n)
begin
if (!rrst_n) rempty <= 1'b1;
else rempty <= rempty_val;
end
//---------------wfull产生与waddr产生------------------------------
always @(posedge wclk or negedge wrst_n) // GRAYSTYLE2 pointer
if (!wrst_n) {wbin, wptr} <= 0;
else {wbin, wptr} <= {wbinnext, wgraynext};
// Memory write-address pointer (okay to use binary to address memory)
assign waddr = wbin;
assign wbinnext = wbin + (winc & ~wfull);
assign wgraynext = (wbinnext>>1) ^ wbinnext; //产生写格雷码
assign wfull_val = (wgraynext=={~wq2_rptr, wq2_rptr}); //:ASIZE-1]
always @(posedge wclk or negedge wrst_n)
if (!wrst_n) wfull <= 1'b0;
else wfull <= wfull_val;
endmodule
同步wptr、rptr是什么意思？那几行代码怎么解释？20-27行
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