3 - ROM - 1 1. ROM What is ROM: Rom is a device that...

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1 1. ROM What is ROM: Rom is a device that includes a decoder and OR gates within a single IC package An input combination is called an address An output patterns is called a word Types of ROM Mask-programmable ROM: programmed at a factory by “masking” Programmable ROM (PROM): One time programmed by the user. PROMs are manufactured with all switches present, and each connection is made by means of a fusible link. These links are selectively blown with current pulses EPROM: Field programmable by a user, programming can be erased and reprogrammed Diagram: Conclusion: ROM with n input lines and m output lines contains an array of 2 n words and each word is m bits long F 0 F 1 F 2 F 3 X1 X2 X3 ROM 8 words X 4 bits 3 input lines 4 output lines Size of ROM: 2 3 words of 4 bits each
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2 ROM stucture n -bit input address sets exactly one of 2 n word lines to 1 Bit pattern stored in this word is transferred to the memory output lines
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3 - ROM - 1 1. ROM What is ROM: Rom is a device that...

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