INTRODUCTION The MR4A08B is a 16,777,216-bit magnetoresistive random access memory (MRAM) device organized as 2,097,152 words of 8 bits. The MR4A08B offers SRAM compatible 35ns read/write timing with unlimited endurance. Data is always non-volatile for greater than 20-years. Data is automatically protected on power loss by lowvoltage inhibit circuitry to prevent writes with voltage out of specification. The MR4A08B is the ideal memory solution for applications that must permanently store and retrieve critical data and programs quickly. The MR4A08B is available in small footprint 400-mil, 44-lead plastic small-outline TSOP type-II package or 10 mm x 10 mm, 48-pin ball grid array (BGA) package with 0.75 mm ball centers. These packages are compatible with similar low-power SRAM products and other non-volatile RAM products. The MR4A08B provides highly reliable data storage over a wide range of temperatures. The product is offered with commercial (0 to +70 °C) and industrial (-40 to +85 °C) operating temperature range options. 存储器的主要功能是存储程序和各种数据,并能在计算机运行过程中高速、自动地完成程序或数据的存取。存储器(Memory)是现代信息技术中用于保存信息的记忆设备。其概念很广,有很多层次,在数字系统中,只要能保存二进制数据的都可以是存储器;在集成电路中,一个没有实物形式的具有存储功能的电路也叫存储器,如RAM、FIFO等;在系统中,具有实物形式的存储设备也叫存储器,如内存条、TF卡等。