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ECT 358 Lecture 18 Memory
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ECT 358 Lecture 18 Memory

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  • 1. ECT 358 Lecture 18 Memory
  • 2.
    • Blessed is he who, having nothing to say, refrains from giving wordy evidence of the fact.
    • The tongue of the wise useth knowledge aright: but the mouth of fools poureth out foolishness.
    • Proverbs 15:2
  • 3. Memory Types
    • Read Only Memory (ROM)
    • Programmable Read Only Memory (PROM)
    • Erasable PROM (EPROM)
    • Electrically Erasable PROM (EEPROM)
    • FLASH
    • Random Access Memory (RAM)
    • Static RAM (SRAM)
    • Ferroelectric Nonvolatile Memory
  • 4. Read Only Memory (ROM)
    • Memory remains unchanged during operation and after power is removed
    • Structurally modified for program
    • Address and Data lines
    • Address Decoder
    • Bipolar/CMOS/nMOS/pMOS
  • 5. Read Only Memory (ROM)
  • 6. Programmable ROM (PROM)
    • Similar structure to ROM
    • One time programmable
    • PROM burner
    • Bipolar technology
    • Can be modified slightly (unburnt fuses)
  • 7. Programmable ROM (PROM)
  • 8. Erasable PROM (EPROM)
    • Similar to PROM
    • Floating nMOS transistor gate
    • Additional gate
    • High programming voltage
    • UV erasable
    • Bulk erase
    • 20 minute erase time
  • 9. Erasable PROM (EPROM)
  • 10. Electrically Erasable PROM (EEPROM)
    • Similar to EPROM
    • Electrically erased vice UV erased
    • Electrical pulses break down gate
    • High negative charge (-15 volts)
    • Programmed in circuit with low voltage
    • Individual words erased
    • 100-100000 erase cycles
    • Much faster than UV for erasing
  • 11. Electrically Erasable PROM (EEPROM)
  • 12. FLASH
    • Similar to EEPROM’s
    • Additional circuitry to selectively erase and program the device in circuit
    • Lower power consumption
    • Simultaneous erasing of blocks
    • Multiple bits per cell (1-3 levels)
    • 100000 erase cycles
  • 13. FLASH
  • 14. Random Access Memory (RAM)
    • Contents changed during operation
    • Data lost when power is removed
    • RAM circuit is fixed, not programmed
    • RAM contents are programmed
    • Requires refresh
  • 15. Static RAM (SRAM)
    • Transistor-Capacitor storage cell structure that does not require refresh
    • Fast Cache
    • 6 transistor circuit
    • Wide input decoder
    • Rectangular versus square physical layout
  • 16. Ferroelectric Nonvolatile Memory
    • Hysteresis effect
    • Electrical polarization under applied voltage
    • Hard Drives
    • Magnetic Tape
    • Floppy Drives
    • Drum Drives
    • Bi-stable states

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