在implementation后出现[DRC MDRV-1] Multiple Driver Nets: Net vgactr/addr_gen_u/Q[0] has multiple drivers: addr_IBUF[0]_inst/O, and vgactr/addr_gen_u/addr_reg[0]/Q.
module addr_gen(
input clk_pix,
input addr_en,
input vsync,
output reg [18:0] addr
);
parameter max_mem=307200;
always@(posedge clk_pix or negedge vsync)
begin
if(!vsync)
addr<=0;
else if(addr_en)
if(addr ==max_mem-1)
addr<=0;
else
addr=addr+1;
end
endmodule