Memory is embedded system's functionality consists of three aspects: processing, storage, and communication. Processing is the transformation of data, storage is the retention of data for later use, and Communication is the transfer of data. Each of these aspects must be implemented. We use processors to implement processing, memory to implement storage, and buses to implement communication.
It has evolved very rapidly over the past few decades. Then the main advancement has been the trend of memory-chip bit-capacity doubling every 18months, following Moore's Law. The importance of this trend in enabling today's sophisticated embedded system should not be underestimated. No matter how fast and complex processors become, those processors still need memories to store programs and to store data to operate on .eg.a digital camera is possible not only because of fast A2D and compression processors but also because of memories capable of storing sufficient quantities of bits to represent the quality picture.
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