Memories

• Larger collections of storage elements

  • implemented not as FFs but as much more efficient latches
  • high-density memories use 1 to 5 switches (transitors) per memory bit

• Static RAM – 1024 words each 4 bits wide

  • once written, memory holds forever (not true for denser dynamic RAM)
  • address lines to select word (10 lines for 1024 words)
  • read enable
    • same as output enable
    • often called chip select
    • permits connection of manychips into larger array
  • write enable (same as load enable)
  • bi-directional data lines
    • output when reading, input when writing

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