如问题代码中所用，与号&"是按位与"运算.

As used in the question code, the ampersand '&' is a bitwise 'and' operation.

示例(假设 VAR_ON = '21'):

Example (assuming that VAR_ON = '21'):

VAR_ON  21(Decimal)    00010101(Binary)
       & 3(Decimal)  & 00000011(Binary)
       ------------  ------------------
         1(Decimal)    00000001(Binary)

因此，如果 VAR_ON 为21"，则表达式 (VAR_ON&3) 的计算结果为1".'if' 条件为假:

Hence if VAR_ON is '21', the expression (VAR_ON&3) will evaluate to '1'. The 'if' condition would be false:

if((VAR_ON&3) > 1)