Computer memory, design and analysis

This paper deals with the design and analysis of a computer memory for space and airborne equipment. A discussion of two basic computer memory technologies and three applications are presented in order to acquaint the reader with memory functions and utility. The two memory technologies discussed are: magnetic memories and semiconductor memories. The three applications discussed are: Scratchpad, permanent/semi-permanent storage, and mass storage. Selection of the type of memory is based on the established requirements and weighted design criteria. The memory that meets all the design requirements and has a minimum weighting factor is the memory selected. The selected memory is a 4K x 20 bit CMOS RAM (Read and Write Memory) and a 8k x 20 bit PROM (Programmable read only memory). Following the selection, memory design proceeds to the conceptual design stage – component selection, memory element configuration and control logic design. In this design, as in most memory designs, the memory is treated as a self-contained unit: that is, a system that generates all its required control signals. Some basic control signals such as memory cycle initiate, address data, input data and mode control (read/write) select are the only input requirements. Memory output requirements consist of output data, data ready and memory busy signals. A thorough analysis is performed on the conceptual design. The analysis demonstrates that the design meets the required specifications. The design analysis is divided into four categories: Timing analysis, Input/Out Loading Analysis, Power Analysis, and Data Retention Switch Analysis. A summary table provides a quick comparison of the analysis results to the original requirements. It also demonstrates at a glance that the memory design meets the established design requirements.