这是按单片机（Microcontrollers）是否提供并行总线来区分的。总线型单片机普遍设置有并行地址总线、 数据总线、控制总线，这些引脚用以扩展并行外围器件都可通过串行口与单片机连接，另外，许多单片机已把所需要的外围器件及外设接口集成一片内，因此在许多情况下可以不要并行扩展总线，大大减省封装成本和芯片体积，这类单片机称为非总线型单片机。(This is based on whether a single chip computer (Microcontrollers) provides a parallel bus. The bus is provided with MCU general parallel address bus, data bus and control bus, these pins for extended parallel peripheral devices can be connected with the microcontroller through the serial port, in addition, many SCM has to the needs of the peripheral device and a peripheral interface integrated on-chip, so in many cases can not parallel expansion bus greatly reduce the packaging cost and chip size, this kind of chip called non bus mcu.)