ERRORXst902Unexpected left_nzc event in always block sensitivity list.

 

在ISE12.4版本中，用ISE自带的综合工具XST综合时出现以下错误：

ERROR:Xst:902 - "nc_calculate.v" line 82: Unexpected left_nzc event in always block sensitivity list.

 

 

源程序：

行82       always@(*)

k_idx,nzc_valid,block_nzc)

begin

                     nT = 0; uT = 0;

                     nL = 0; uL = 0;

                     if(is_luma)

                     begin

                            case(block_idx)

                            4'h0: begin nT = top_nzc[0]; nL = left_nzc[0]; uT=1; uL=1; end

              ……..

 

解决办法：

1、将always@(*)改为 always@(aaa) aaa为begin end块内等号右边的所有变量和begin end块中所有input变量

如： always@(is_luma or block_idx or top_nzc[0] or .....)

2、将所用器件改为 family:Virtex6 Device:XC6VLX240T。原来为Virtex5。 

下面来看：

always@(*) 指的是对 其后面语句块中所有的输入变量的变化时敏感的。

Always@(*) 和always@*的区别：

 

Example 1

always @(*) // equivalent to @(a or b or c or d or f)

y = (a & b) | (c & d) | myfunction(f);

 

Example 2

always @* begin // equivalent to @(a or b or c or d or tmp1 or tmp2)

tmp1 = a & b;

tmp2 = c & d;

y = tmp1 | tmp2;

end

 

Example 3

always @* begin // equivalent to @(b)

@(i) kid = b; // i is not added to @*

End

 

Example 4

always @* begin // equivalent to @(a or b or c or d)

x = a ^ b;

@* // equivalent to @(c or d)

x = c ^ d;

end