1. 操作数在寄存器中，R0--R7

2. 操作数在内RAM中

3. 操作数在外RAM中

不过都大同小异，以2例,是个乘法子程序。

入口：乘数R0，被乘数R1，字节数R7，结果在R0-1. Operands in the registers, R0- R7 2. Operand, including RAM, 3. Operand out RAM, but are similar to two cases, is a multiplication subroutine. Entrance: multiplier R0, multiplicand R1, the number of bytes R7, result in R0