一、前言众所周知,在小型专用数字计算机中,为了提高可靠性,兼顾灵活性和经济性,除了活动存贮器外,还采用固定存贮器,用以存放常用程序和常数。固定存贮器所存信息内容是不变的,因而在制造过程中就可将信息预先写入存贮体内固定起来,以后计算机工作时只是读出,不再需要重写,从而在结构上比一般活动存贮器简单得多,使机器变得可靠而经济。固定存贮器的种类繁多,除了常见的变压器磁芯、螺线管、磁棒、双轴磁芯等固定存贮器之外,还有电容、二极管矩阵等固定存贮器。目前,半导体只读存贮器也获得了迅速发展,当前已能提供使用的有采用掩模技术的半导体只读存贮器和熔丝型半导体只读存贮器,此外, I. INTRODUCTION As we all know, in order to improve the reliability and balance the flexibility and economy of small dedicated digital computers, in addition to the active memory, a fixed memory is also used to store commonly used programs and constants. The contents of fixed memory stored information is unchanged, so in the manufacturing process can be pre-written information stored in the body fixed up, after the computer is only read out the work, no longer need to rewrite, so that the structure than the average The moveable memory is much simpler, making the machine reliable and economical. A wide range of fixed memory, in addition to the common transformer core, solenoid, bar, biaxial core and other fixed memory, there are capacitors, diode matrix and other fixed memory. At present, there has also been a rapid development of semiconductor ROMs, and there are currently available semiconductor ROMs and fuse type semiconductor ROMs using a mask technology. In addition,