What is Memory -
- A physical device capable of storing information
- Temporary information storage - RAM ( Information gets lost on Power Down)
- Permanently information storage - Read Only Memory (ROM)
- Memory devices are made of integrated circuits and are used by hardware , operating systems and softwires
- Three main processes involved in Memory : Encoding , Storage and Retrieval
Design of Memory Unit -
- A Memory Unit is a collection of storage cells together with their associated integrated circuits to transfer information in and out of the memory device.
- Below is the top level block diagram of a Memory Unit
- The construction of a M*N (M Words with N Bits Per Word) consists of M*N Binary Storage Cells and associated decoding circuits for selecting individual words
Binary Cell -
- The 'Select' input Enables the Cells for Reading or Writing
- Read/Write Bar == 1, Reading the Binary Cell by Making a Path Between Flip-Flop to Output
- Read/Write Bar == 0, Writing the Binary Cell by forming a Path from Input to flip-Flop
Design of a 4*4 Memory -
- 4*4 Memory with 4 Word Lines of 4 Bits each with a total of 16 Binary Storage Cells
- 2 Address Lines are needed for a 4 words memory
- Address lines are decoded using a Decoder with 'Memory Enable' signal
- Once a particular word line is 'selected', the 'Read/Write bar' signal determines the memory operation
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