9-Memory - III

9-Memory - III - Memory - III Presenter Tathagata...

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Memory - III Presenter Tathagata Bhattacharjee
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Tathagata Bhattacharjee 2 Random Access Memory Two basic forms of semiconductor random-access memory are Dynamic RAM (DRAM) Static RAM (SRAM) SRAM is faster, more expensive and less dense than DRAM SRAM used in cache memory DRAM used in main memory
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Tathagata Bhattacharjee 3 Semi conductor Main Memory Organization The basic element of a semiconductor memory is the memory cell All semiconductor memory cells share certain properties They exhibit two stable states, which can be used to represent binary 1 and 0 They are capable of being written into (at least once) to set the state They are capable of being read to sense the state
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Tathagata Bhattacharjee 4 Memory Cell Operation
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Tathagata Bhattacharjee 5 Cell has three terminals capable of carrying an electrical signal The select terminal selects a memory cell for a read or write operation The control terminal indicates read or write For writing the terminal provides an electrical signal that sets the state of the cell to 1 or 0 For reading the terminal used for output of the cell’s state
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Tathagata Bhattacharjee 6 Semiconductor Memory Types
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Tathagata Bhattacharjee 7 Semiconductor Memory RAM Misnamed as all semiconductor memory is random access Read/Write Volatile Temporary storage Static or Dynamic
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Tathagata Bhattacharjee 8 Dynamic RAM Bits stored as charge in capacitors Charges leak Need refreshing even when powered Simpler construction Smaller per bit Less expensive Need refresh circuits Slower Main memory Essentially analogue Level of charge determines value
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Tathagata Bhattacharjee 9 Dynamic RAM Structure
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Tathagata Bhattacharjee 10 The diagram shows an individual cell that stores one bit The address line is activated when the bit value from the cell is to be read or written The transistor acts as a switch Closed (allowing current to flow) if voltage is applied to the address line Open (no current flows) if no voltage is present on the address line
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Tathagata Bhattacharjee 11 For write operation , a voltage signal is applied to the bit line High voltage represents 1 Low voltage represents 0 A signal is then applied to the address line, allowing a charge to be transferred to the capacitor
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12 For read operation, when the address line is selected, The transistor turns on and the charge stored on the capacitor is fed out onto a bit line and to a sense amplifier The sense amplifier compares the capacitor voltage to a reference value and determines if the cell contains a logic 1 or a logic 0
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This note was uploaded on 07/15/2011 for the course ECO 2023 taught by Professor Mr.raza during the Summer '10 term at FAU.

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9-Memory - III - Memory - III Presenter Tathagata...

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