- first in first out,先进先出
- fifo是基于RAM进行设计的
双端口RAM设计(16*8)
- 如果大的RAM可以调用IP
- RAM的关键参数:深度和宽度
module dual_ram
#(
parameter ADDR_WIDTH = 4,
parameter RAM_WIDTH = 8,
parameter DLY=1
)
(
input wire read_clk ,
input wire write_clk ,
input wire [ADDR_WIDTH-1:0] read_addr ,
input wire [ADDR_WIDTH-1:0] write_addr ,
input wire read_allow ,
input wire write_allow ,
input wire [RAM_WIDTH-1:0] write_data ,
output reg [RAM_WIDTH-1:0] read_data
);
reg [RAM_WIDTH-1:0] memory [ADDR_WIDTH-1:0];
always @(posedge read_clk) begin
if(read_allow)
read_data <= #DLY memory[read_addr];
end
always @(posedge write_clk) begin
if(write_allow)
memory[write_addr] <= #DLY write_data;
end
endmodule
单端口ram
module single_port_ram
#(
parameter ADDR_WIDTH = 8,
parameter RAM_WIDTH = 8,
parameter RAM_DEPTH = 255,
parameter DLY = 1
)
(
input wire clk,
input wire rst_n,
input wire [ADDR_WIDTH-1:0] addr,
input wire wr_en, // 1-write 0-read
input wire [RAM_WIDTH-1:0] wdata,
output wire [RAM_WIDTH-1:0] rata
);
reg [RAM_DEPTH-1:0] mem [RAM_WIDTH-1:0];
integer i;
always @(posedge clk or negedge rst_n) begin
if(rst_n)
for(i=0;i<=255;i=i+1) begin
mem[i] = 16'h0000;
end
else if(wr_en)
mem[addr] <= wdata;
end
assign radta = (!wr_en) ? mem[addr] : 16'h0000 ;
// always @(posedge clk or negedge rst_n) begin
// if(!rst_n)
// radta <= 'h0;
// else if(!wr_en)
// r_data <= mem[addr];
// end
endmodule
同步FIFO设计
module sync_fifo
#(
parameter ADDR_WIDTH = 9,
parameter RAM_WIDTH = 8
)
(
input wire fifo_clk,
input wire fifo_rst_n,
input wire read_en,
input wire write_en,
input wire [RAM_WIDTH-1:0] w_data,
output wire [RAM_WIDTH-1:0] r_data,
output reg empty,
output reg full,
output reg [ADDR_WIDTH-1:0] fcounter
);
reg [ADDR_WIDTH-1:0] write_addr;
reg [ADDR_WIDTH-1:0] read_addr;
wire write_allow = write_en && (!empty);
wire read_allow = read_en && (!full);
// empty
always @(posedge fifo_clk or negedge fifo_rst_n) begin
if(fifo_rst_n)
empty <= 1'b1;
else
empty <= (!write_allow) && (fcounter[ADDR_WIDTH-1:1] == 8'h0) && (fcounter[0] == 0||read_allow);
end
// full
always @(posedge fifo_clk or negedge fifo_rst_n) begin
if(fifo_rst_n)
full <= 1'b0;
else
full <= (!read_allow) && (fcounter[ADDR_WIDTH-1:1] == 8'hff) && (fcounter[0] == 1||write_allow);
end
always @(posedge fifo_clk or negedge fifo_rst_n) begin
if(fifo_rst_n)
fcounter <= {ADDR_WIDTH{1'b0}};
else if( (!read_allow) && (write_allow)||(read_allow) && (!write_allow)) begin
if(write_allow)
fcounter <= fcounter + 1'b1;
else
fcounter <= fcounter - 1'b1;
end
end
always @(posedge fifo_clk or negedge fifo_rst_n) begin
if(fifo_rst_n)
write_addr <= {ADDR_WIDTH{1'b0}};
else if(write_allow)
write_addr <= write_addr + 1'b1;
end
always @(posedge fifo_clk or negedge fifo_rst_n) begin
if(fifo_rst_n)
read_addr <= {ADDR_WIDTH{1'b0}};
else if(write_allow)
read_addr <= read_addr + 1'b1;
end
dual_ram u_dual_ram
(
.read_clk (fifo_clk),
.write_clk (fifo_clk),
.read_addr (read_addr),
.write_addr (write_addr),
.read_allow (read_allow),
.write_allow (write_allow),
.write_data (w_data),
.read_data (r_data)
);
endmodule
module sync_fifo
#(
parameter ADDR_WIDTH = 4,
parameter RAM_WIDTH = 8,
parameter RAM_DEPTH = 16,
)
(
input wire fifo_clk,
input wire fifo_rst_n,
input wire read_en,
input wire write_en,
input wire [RAM_WIDTH-1:0] w_data,
output wire [RAM_WIDTH-1:0] r_data,
output reg empty,
output reg full
);
// 指针
reg [ADDR_WIDTH:0] write_addr;
reg [ADDR_WIDTH:0] read_addr;
wire [ADDR_WIDTH-1:0] w_addr;
wire [ADDR_WIDTH-1:0] r_addr;
wire write_allow = write_en && (!empty);
wire read_allow = read_en && (!full);
reg [RAM_WIDTH-1:0] mem [RAM_DEPTH-1:0];
always @(posedge fifo_clk or negedge fifo_rst_n) begin
if(!fifo_rst_n)
read_addr <= {ADDR_WIDTH{1'b0}};
else if(read_allow) begin
r_data <= mem[read_addr];
read_addr <= read_addr + 1;
end
end
always @(posedge fifo_clk or negedge fifo_rst_n) begin
if(!fifo_rst_n)
write_addr <= {ADDR_WIDTH{1'b0}};
else if(write_allow) begin
mem[write_addr] <= w_data;
write_addr <= write_addr + 1;
end
end
assign empty = read_addr == write_addr ? 1 : 0;
assign full = (read_addr[ADDR_WIDTH]!=write_addr[ADDR_WIDTH]) &&
(read_addr[ADDR_WIDTH-1:0] == write_addr[ADDR_WIDTH-1:0]);
assign r_addr = read_addr[ADDR_WIDTH-1:0]
assign w_addr = write_addr[ADDR_WIDTH-1:0]
endmodule