说明：  用VHDL语言描述和实现乘法累加器设计,4位的被乘数X和4位的乘数Y输入后，暂存在寄存器4位的寄存器A和B中，寄存器A和B的输出首先相乘，得到8位乘积，该乘积再与8位寄存器C的输出相加，相加结果保存在寄存器C中。寄存器C的输出也是系统输出Z。(原创，里面有乘法部分和累加部分可以单独提出来，很好用)
(With the VHDL language to describe the design and realization of multiplier-accumulator, four of multiplicand X and 4-bit multiplier Y input, the temporary 4-bit registers in the register A and B, registers A and B multiplied by the output of the first, to be 8-bit product, the product further with the 8-bit output of register C, the sum of, the sum of the results stored in register C,. The output register C is also the system output Z. (Original, which are multiply and accumulate some part may be raised separately, very good use))