XST和synplify综合出的结果完全不一致

只看该作者 · 2016-11-10 15:41

用的是xillinx的XC2C32A，很老的CPLD。就是一个流水灯小程序。XST能实现流水灯显示。但是在synplify综合后，4个LED一直常亮。到底是哪里的问题呢？
代码如下：
module Main(
iCLK,
      oLED
      );

input iCLK;
output [3:0]oLED;

reg [24:0]sr_counter = 25'b0;
reg [3:0]sr_led = 4'b1110;

assign oLED = sr_led;

always@(posedge iCLK)
      if(sr_counter >= 25'd25000000)
            sr_counter <= 1'b0;
      else
            sr_counter <= sr_counter + 1'b1;

always@(posedge iCLK)
      if(sr_counter >= 25'd25000000)
            sr_led <= {sr_led[2:0],sr_led[3]};
      else
            sr_led <= sr_led;

endmodule