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How to use AT28C64B? Answered

I am making an 8-Bit Computer for a science fair project. I have everything working, but there is one problem. Everything action has to be done manually. It could work this way but I want to be able to write a program, press a button, and the computer will do the rest. To do this I have to use a control matrix to control the Input/output of each device to the bus. To do this I will use an EEPROM. However, I am using TTL logic and the AT28C64B is CMOS, but it has TTL and CMOS logic compatible Inputs and Outputs. When I programed it, I did WE low OE high and CE low. When I read from it I had WE high, OE low and CE low. When I had CE plugged into nothing which I think is High-Z, I noticed just a brightness difference between 0 and 1 on the LEDs. When I plugged the Chip Enable(CE) into ground it made every LED the same brightness so that you could not tell the difference. For my TTL logic I need either voltage or ground to control 1 or 0. Am I doing something wrong? Please help me! I really need the help.

Tags:EEPROM

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steveastrouk

Best Answer 2 years ago

You need to show a circuit diagram/schematic. WHAT leds, where are they connected ?

You can't say what state CE is in if it isn't connected ! It is probably floating randomly.

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BeauH3steveastrouk

Answer 2 years ago

I do not have a schematic, I am hooking the output up to 8 blue LEDs, I program the chip, then I rewire the I/O pins to the LEDs and they do not have an on/off state, they just show whether it is bright, or less bright for 1 or 0. I am new to CMOS technology, do I have to do something different compared to TTL.

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steveastroukBeauH3

Answer 2 years ago

For a start, CMOS inputs float, they can't be assumed to be high or low, hence your problem.

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BeauH3steveastrouk

Answer 2 years ago

Well I know I have the CE, WE, and OE hooked up correctly. I am just wondering why the chip will not drive the LEDS to be on or off. I tried Tri-State Buffers with the enable attached to ground so that it will always make an output, but it still did not make a difference, why is this?

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BeauH3steveastrouk

Answer 2 years ago

I got it to work. I just hooked the unused address lines to ground. They were not working because the address was floating. Thank you for the CMOS tips.

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steveastroukBeauH3

Answer 2 years ago

Well done !

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