Random Access Memory (Ram)

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Random access memory
• Sequential circuits all depend upon the presence of memory. – A flip-flop can store one bit of information. – A register can store a single “word,” typically 32-64 bits. • Random access memory, or RAM, allows us to store even larger amounts of data. Today we’ll see: – The basic interface to memory. – How you can implement static RAM chips hierarchically. This is the last piece we need to put together a computer!



Random Access Memory

1

Introduction to RAM
• Random-access memory, or RAM, provides large quantities of temporary • storage in a computer system. Remember the basic capabilities of a memory: – It should be able to store a value. – You should be able to read the value that was saved. – You should be able to change the stored value. A RAM is similar, except that it can store many values. – An address will specify which memory value we’re interested in. – Each value can be a multiple-bit word (e.g., 32 bits). We’ll refine the memory properties as follows: A RAM should be able to: - Store many words, one per address - Read the word that was saved at a particular address - Change the word that’s saved at a particular address

• •

Random Access Memory

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Picture of memory
• You can think of computer memory as being one big array of data. – The address serves as an array index. – Each address refers to one word of data. You can read or modify the data at any given memory address, just like you can read or modify the contents of an array at any given index. If you’ve worked with pointers in C or C++, then you’ve already worked with memory addresses.





Random Access Memory

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Block diagram of RAM
2k x n memory k n

ADRS DATA CS WR

OUT

n

• This block diagram introduces the main interface to RAM. – A Chip Select, CS, enables or disables the RAM. – ADRS specifies…...

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