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Memory

Memory. Memory. Memory Types Using memory to implement logic functions. Memory Types. “Any sequential circuit has memory of a sort, since each flip-flop or latch stores one bit of information”

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Memory

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  1. Memory ECE 561 - Lecture

  2. Memory • Memory Types • Using memory to implement logic functions ECE 561 - Lecture

  3. Memory Types • “Any sequential circuit has memory of a sort, since each flip-flop or latch stores one bit of information” • The term memory is usually reserved for that part of a system where bits of information is stored in a structured way. This is usually a 2-dimensional array in which one row of bits is accessed. ECE 561 - Lecture

  4. Read Only Memory (ROM) • ROM is a combinational circuit with n inputs and b outputs. The n inputs are the address and usually called A0 A1 A2 A3 * * *. The outputs are usually called D0 D1 * * *. • At each of the 2n unique addresses permanently stores a b bit value ECE 561 - Lecture

  5. ROM as a logic element • ROM is memory but it is also a combination element. • As a combination element it can perform logic functions. • Table 9-1 versus combination logic for implementation. ECE 561 - Lecture

  6. Table 9-1 • The truth table ECE 561 - Lecture

  7. Implementation • Have Table 9-1 • Work out logic equations and construct circuit • How many logic gates does it take? • What is the delay using logic gates? • What is the delay using ROM? • Data sheet for ROM show timing ECE 561 - Lecture

  8. ROM Programming • ROM – value at each storage location is “stored” when the ROM is manufactured. • ROM is non-volatile memory • PROM – Programmable Read Only Memory • Using a programmer the values are written after manufacture. • Types of PROMs • One time programmable – fuseable links • UV EPROM – The E stands for Erasable • EEPROM – Electrically Erasable PROM ECE 561 - Lecture

  9. ROMs for combination logic • Section 9.1.1 ROMs for “random” combinational logic. ECE 561 - Lecture

  10. The solution using ROM Use an 8 x 4 PROM 3 inputs are A0, A1, and POL 4 outputs are Y0, Y1, Y2, and Y3 What is the programming table??? ECE 561 - Lecture

  11. Another problem • Build a 4 x 4 binary multiplier • Combination logic requirements • Versus a ROM implementation • Remember our PROM and its timing? ECE 561 - Lecture

  12. Can implement in Gates • Work out logic equations and then how many gates/units does it take? • Time?? • Or could implement in ROM ECE 561 - Lecture

  13. Resulting PROM Programming ECE 561 - Lecture

  14. Assignment • Due Monday Nov 3rd • Go to www.wikipedia.com and look up PROM, EPROM, UV EPROM and EEPROM. Write a ½ to 1 page write up summarizing the information you find there. • Go to www.digikey.com and look up the price and features for 2 PAL chips, 2 PLA chips, and 2 FPGAs. Write a ½ to 1 page summary of this. • Tuesday Nov 4th – VOTE!!!!!!!!! • Due Wednesday Nov 5th • Problem 9.1 but only do 6-37 and 6-73. Also, show the signals on the address inputs and the data outputs. ECE 561 - Lecture

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  19. Solution • The solution Table 9-2 and Fig 9-4 ECE 561 - Lecture

  20. ECE 561 - Lecture

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