異步FIFO問題 二
阿新 • • 發佈:2018-03-10
數據 data code inpu rda emp 存儲 address ext
同步FIFO, verilog:
module fifo(clock,reset,read,write,fifo_in,fifo_out,fifo_empty,fifo_half,fifo_full);
input clock,reset,read,write;
input [15:0]fifo_in;
output[15:0]fifo_out;
output fifo_empty,fifo_half,fifo_full;//標誌位
reg [15:0]fifo_out;
reg [15:0]ram[15:0];
reg [3:0]read_ptr,write_ptr,counter;//指針與計數
wire fifo_empty,fifo_half,fifo_full;
always@(posedge clock)
if(reset)
begin
read_ptr=0;
write_ptr=0;
counter=0;
fifo_out=0; //初始值
end
else
case({read,write})
2‘b00:
counter=counter; //沒有讀寫指令
2‘b01: //寫指令,數據輸入fifo
begin
ram[write_ptr]=fifo_in;
counter=counter+1;
write_ptr=(write_ptr==15)?0:write_ptr+1;
end
2‘b10: //讀指令,數據讀出fifo
begin
fifo_out=ram[read_ptr];
counter=counter-1;
read_ptr=(read_ptr==15)?0:read_ptr+1;
end
2‘b11: //讀寫指令同時,數據可以直接輸出
begin
if(counter==0)
fifo_out=fifo_in;
else
begin
ram[write_ptr]=fifo_in;
fifo_out=ram[read_ptr];
write_ptr=(write_ptr==15)?0:write_ptr+1;
read_ptr=(read_ptr==15)?0:write_ptr+1;
end
end
endcase
assign fifo_empty=(counter==0); //標誌位賦值 組合電路
assign fifo_half=(counter==8);
assign fifo_full=(counter==15);
endmodule
異步FIFO實現:
module fifo1(rdata, wfull, rempty, wdata, winc, wclk, wrst_n,rinc, rclk, rrst_n);
parameter DSIZE = 8; parameter ASIZE = 4;
output [DSIZE-1:0] rdata;
output wfull;
output rempty;
input [DSIZE-1:0] wdata;
input winc, wclk, wrst_n;
input rinc, rclk, rrst_n;
reg wfull,rempty;
reg [ASIZE:0] wptr, rptr, wq2_rptr, rq2_wptr, wq1_rptr,rq1_wptr;
reg [ASIZE:0] rbin, wbin;
reg [DSIZE-1:0] mem[0:(1<<ASIZE)-1];
wire [ASIZE-1:0] waddr, raddr;
wire [ASIZE:0] rgraynext, rbinnext,wgraynext,wbinnext;
wire rempty_val,wfull_val;
//-----------------雙口RAM存儲器--------------------
assign rdata=mem[raddr];
always@(posedge wclk)
if (winc && !wfull) mem[waddr] <= wdata;
//-------------同步rptr 指針-------------------------
always @(posedge wclk or negedge wrst_n)
if (!wrst_n) {wq2_rptr,wq1_rptr} <= 0;
else {wq2_rptr,wq1_rptr} <= {wq1_rptr,rptr};
//-------------同步wptr指針---------------------------
always @(posedge rclk or negedge rrst_n)
if (!rrst_n) {rq2_wptr,rq1_wptr} <= 0;
else {rq2_wptr,rq1_wptr} <= {rq1_wptr,wptr};
//-------------rempty產生與raddr產生-------------------
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[ASIZE-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)
begin
if (!rrst_n) rempty <= 1‘b1;
else rempty <= rempty_val;
end
//---------------wfull產生與waddr產生------------------------------
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[ASIZE-1:0];
assign wbinnext = wbin + (winc & ~wfull);
assign wgraynext = (wbinnext>>1) ^ wbinnext;
assign wfull_val = (wgraynext=={~wq2_rptr[ASIZE:ASIZE-1], wq2_rptr[ASIZE-2:0]}); //:ASIZE-1]
always @(posedge wclk or negedge wrst_n)
if (!wrst_n) wfull <= 1‘b0;
else wfull <= wfull_val;
endmodule
異步FIFO問題 二