1. Memory 10/27/081ECE 561 - Lecture

2. Memory Memory Types Using memory to implement logic functions 10/27/082ECE 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. 10/27/083ECE 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 A 0 A 1 A 2 A 3 * * *. The outputs are usually called D 0 D 1 * * *. At each of the 2 n unique addresses permanently stores a b bit value 10/27/084ECE 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. 10/27/08ECE 561 - Lecture5

6. Table 9-1 The truth table 10/27/08ECE 561 - Lecture6

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 10/27/08ECE 561 - Lecture7

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 10/27/08ECE 561 - Lecture8

9. ROMs for combination logic Section 9.1.1 ROMs for “random” combinational logic. 10/27/08ECE 561 - Lecture9

10. The solution using ROM 10/27/08ECE 561 - Lecture10 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???

11. Another problem Build a 4 x 4 binary multiplier Combination logic requirements Versus a ROM implementation Remember our PROM and its timing? 10/27/08ECE 561 - Lecture11

12. Can implement in Gates Work out logic equations and then how many gates/units does it take? Time?? Or could implement in ROM 10/27/08ECE 561 - Lecture12

13. Resulting PROM Programming 10/27/08ECE 561 - Lecture13

14. Assignment Due Monday Nov 3 rd – 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.www.digikey.com Tuesday Nov 4 th – 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. 10/27/08ECE 561 - Lecture14

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19. Solution The solution Table 9-2 and Fig 9-4 10/27/08ECE 561 - Lecture19

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