SDRAM刷新程序实例
`include "camera_head.v"
module refresh (pi_clk, pi_rst_n, po_refresh_bus, po_refresh_done);
// system
input pi_clk;
input pi_rst_n;
// out
output po_refresh_bus;
output po_refresh_done;
//------------------------------------------------------------
reg commands;
reg sdram_bank;
reg sdram_addr;
assign po_refresh_bus = commands;
assign po_refresh_bus = sdram_bank;
assign po_refresh_bus = sdram_addr;
//-----------------------------------------------------------
reg state;
reg cnt;
reg po_refresh_done;
always @ (posedge pi_clk, negedge pi_rst_n)
begin
if (!pi_rst_n)
begin
state <= 2'd0;
commands <= `NOP;
cnt <= 3'd0;
sdram_addr <= 12'd0;
sdram_bank <= 2'd0;
po_refresh_done <= 1'b0;
end
else
begin
case (state)
0 : begin
commands <= `PREC;
sdram_addr <= 1'b1;
state <= 1;
end
1 : begin
if (cnt < 2)
begin
commands <= `NOP;
cnt <= cnt + 1'b1;
end
else
begin
commands <= `REF;
cnt <= 3'd0;
state <= 2;
end
end
2 : begin
if (cnt < 7)
begin
cnt <= cnt + 1'b1;
commands <= `NOP;
end
else
begin
cnt <= 3'd0;
commands <= `REF;
state <= 3;
end
end
3 : begin
if (cnt < 7)
begin
cnt <= cnt + 1'b1;
commands <= `NOP;
end
else
begin
state <= 3;
po_refresh_done <= 1'b1;
end
end
default : state <= 0;
endcase
end
end
endmodule SDRAM刷新程序实例
页:
[1]
