鉴于MCS-51系统只提供“二级中断嵌套”，提出扩展51系统中断优先级的纯软件方法。其利用51系统内建的中断允许寄存器IE和中断优先级寄存器IP，通过屏蔽字机制来实现；以C51的形式，给出这种扩展方法的函数库实现，为该方法的使用赋予友好、简洁的用户接口。-Given MCS-51 systems only provide "two interrupt nesting," expanded 51 priority system interruption of pure software. The use of 51 built-in system allows interruption Register IE and priority interrupt register IP, through word shielding mechanisms to achieve; C51 in the form of this expansion is the way to achieve functions, methods for the use of empowerment friendly, simple user interface.