关于寄存器的操作

Register operations – small numbers (-64 <= num <= +63)
R0 += small_num; // Note: affects AZ bit
R0 += 6; // OK
R0 += -8; // OK
R0 = R0 + 6; // NOT

Register operations – larger numbers
R1 = larger_num;
R0 = R0 + R1;  // OK
R0 += R1; // NOT
R1.L = lo(40000);
R1.H = hi(40000);
R0 = R0+R1;

上面的操作是指数字小的话要用这种类型R0 += small_num;
数字大的话用R0 = R0 + R1;  
为什么呢

感觉是对固定数值操作时，用 +=   ，对寄存器操作时  用 = 。