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CSET 4650 Field Programmable Logic Devices

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Presentation on theme: "CSET 4650 Field Programmable Logic Devices"— Presentation transcript:

1 CSET 4650 Field Programmable Logic Devices
Logic Implementation Using Programmable ROMs CSET Field Programmable Logic Devices For additional information, contact any of the following individuals: Dan Solarek Professor and Chairman Voice: Allen Rioux Director of Online Services To leave a message for any of these individuals call the department secretary at You may send a FAX to Dan Solarek Richard Springman Director of Student Services Voice: Myrna Swanberg Academic Program Coordinator Voice:

2 Programmable Read Only Memory
A ROM is a memory device that holds a fixed, addressable data set A PROM may be programmed by the designer UV erasable PROM

3 Programmable Read Only Memory
Typical uses include: Code converters Character generators Data storage tables Program stores Loaded with tabular data – not Boolean equations e.g., a truth table

4 Conceptual PROM Architecture
32x8 PROM 5-to-32 decoder 8 OR gates with 32 inputs 32x8 internal programmable connections k = 5 2k = 32 programmable OR connections output word (8-bits)

5 Conceptual PROM Architecture
A PROM has a fixed AND array (that decodes the memory address) followed by a programmable OR array (outputs) For each of a given set of input combinations (address), it generates a multi-bit value which has been programmed into the device

6 Using PROMs as PLDs The output functions need to be expressed in canonical minterm form for PROM implementation every input variable appears in each product term in its true or inverted form Each minterm is used to represent an address Each address generates a multi-bit output

7 Realistic PROM Architecture
decoder logic A PROM has a fixed AND array and a programmable OR array Remember, we are only programming the CONNECTIONS to the OR gates AND gate connections are all possible combinations

8 Simplified PROM Architecture
Inputs A and B true and inverted Outputs Y and Z e.g., two functions Programmable connections to OR gates 0 0 0 1 1 0 1 1

9 Example 7-11 from Sandige Binary to hex character generator
OA OC OD OE OB OF OG Binary to hex character generator Using a seven-segment display device and the character scheme at right

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