8_PROM_Slides

8_PROM_Slides - ECE ECE 3504 Digital Design 1 Section 8:...

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ECE 3504 Digital Design 1 Section 8: Circuit Prototyping using PROMs
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Memory Characteristic Memory Characteristics In general, a memory module a memory module having 2 k addresses and m bits per address requires k address lines to h f t h 2 k dd choose one of the 2 addresses, and m data lines to carry the information of a particular address. In a read-only memory, the address lines are inputs , and the data lines are output are outputs .
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Memory Characteristic Memory Characteristics This 32×4 PROM has 5 address lines and 4 data lines lines and 4 data lines. The address lines have a predetermined order of significance. The data lines have a nominal order of significance order of significance.
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Architectural Representation Recall the architectural Recall the architectural representation of PLA circuits. In a programmable ROM , the AND array is fixed and the OR array is programmable .
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Programmable ROM Programmable ROMs (Address Inputs) (Data Outputs)
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Programmable ROM Programmable ROMs The previous circuit implements a The previous circuit implements a 16 × 3 PROM. The AND array is such that only one of the AND gates will supply an output of 1 for a particular combination of the address inputs. An OR gate will supply an output of 1 if the user connects one of th OR t ’ i t t AND the OR gate’s inputs to an AND gate whose output is 1. Consider that the unused OR gate inputs receive inputs of 0.
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Programmable ROM Programmable ROMs
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Wait what Wait…what? A PROM is a combinational circui A PROM is a combinational circuit. How can a combinational circuit act as a memory device? More to the point, how can a combinational circuit act as a non- volatil memory device volatile memory device?
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Using PROMs in Combinational Circuits Since a PROM is fundamentally a Since a PROM is fundamentally a combinational circuit, we can use PROMs to implement bi ti l f ti combinational functions. We can use the address lines to carry the inputs of the functions, and the data lines to supply the outputs of the functions.
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This note was uploaded on 01/17/2011 for the course ECE 3504 at Virginia Tech.

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8_PROM_Slides - ECE ECE 3504 Digital Design 1 Section 8:...

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