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Decode: EEPROM Overkill

A project log for DDL4-CPU

A Modular 4-Bit CPU Design

daves-dev-labDave's Dev Lab 05/24/2018 at 03:190 Comments

Two modules assembled... six to go! The Decode Module was the next easiest one to assemble, so I figured I would complete it this evening. It uses the same Low Insertion Force (LIF) sockets as on the ROM Module, as well as the same Atmel 8k x 8 eeprom. Using the 8k x 8 eeprom is extreme overkill for the decode module, however, since I was already purchasing some of the Atmel eeproms, I could use them for the Decode Module as well. I think in future versions I might go with a smaller eeprom, or even a small CPLD. This module consists of the two eeproms, a 74LVC193 4-bit counter tied to a 74LVC138 1-of-8 decoder. These two combine to control each of the 7 phases of the microprogramming. I've added LEDs to indicate the phase state as well as some LEDs to display the primary clock status. This module connects to 4 other modules, more than any other, so I decided to use female headers on all four sides.

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