为什么步长只能为1？

只看该作者 · 2010-9-20 16:56

顶层模块——
module ramout(

input       clkin,
input [7:0]  addr_read,
output  [11:0] data_read );

reg  [ 7:0] cnt;
reg  [ 1:0] status;

reg  [ 7:0] addr;
reg  [15:0] din;
wire [15:0] dout;
reg       we;

assign data_read = dout[11:0];

ram1 ram11(.addr(addr),
   .clk(clkin),
   .din(din),
   .dout(dout),
   .we(we)
   );

always@(negedge clkin)
if(cnt != 8'd166) cnt <= cnt + 8'd1;

always@(negedge clkin)
if(cnt < 8'd6) status <= 2'd0;
else if(cnt != 8'd166) begin
   status <= 2'd1;
we    <= 1'b1;
din <= din + 16'd2; //递增2就不行
addr <= addr + 8'd1;      end
else begin status <= 2'd2;
we    <= 1'b0;    end

always@(negedge clkin)
if(status == 2'd2 && addr_read < 8'd166)    addr  <= addr_read;

endmodule
片上ram为16位宽，深度256。
自动生成数写入片上ram时，递增1就可以，递增2或3时就报错——
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr_cy<0>>
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr2>
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr4>
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr6>
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr8>
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr10>
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr12>
ERROR:Xst:528 - Multi-source in Unit <myad> on signal <Mcount_addr14>
为什么？
求高手指点！先谢过！