AT28C16 EEPROM learning experiments

[_q12x_]

Thanks to mister -marconi , I received his chip AT28C16 gift from England !
I will start to make the 5x7 led matrix project that you did.
I will make it alone as much as I can (as usual). And I will ask you for clarifications on the way.

 

[_q12x_]

I remember last night when it worked, I had this arrangement from original experiment.
It was not doing anything important so I remove it today.
I start to believe it was affecting the circuit.

All the switches are turn off, and all the addr pins are pull down by those blue resistors on top near the blue DIP switch.
Ive already put resistors to gnd on each addr pin but no effect, it didnt repaired the problem.

 

[marconi]

Just check your power supply voltage at the Vcc and 0V pins of the 7493 bottom left.

Also check voltage drop between power supply output terminals and the 7493 Vcc and 0V pins ie: PSU 5V to 93 Vcc and PSU 0V and 0V.

 

[_q12x_]

every voltage from 7493 to addr pins are fine, it is counting fine, no problem there.
the memory is affected by something....

 

[marconi]

If you have removed the eeprom just check its pins have not been bent underneath it when reinserted.

check CEbar and OEbar pins are connected to correct 0V rail.

check WEbar is not floating but connected to push button pulse circuit and should normally be logic 1.

check eeprom has been reinserted correctly to align pins with breadboard connections.

check scan clock is at 1000hz or lower.

 

[_q12x_]

Nope , problem solved ! Thank you for the ideas !

 

[_q12x_]

here it is:

 

[_q12x_]

And here I am showing how to program some letters and also switch one after another.
Do take a look at this beauty: aaah

Thank you very much so far !!!

 

[_q12x_]

Thanks for the medal

mister @marconi; it was hard for me because I actually had to think what to do and how to do it and also resolve all the errors that appear on the way. Some seem unsolvable without my good friends help. I took it very slow because I had to get used to these logic gates, get experience with them, also the counter IC's and the memory itself. it was very hard project to deal but I learned and most important I got experience and I understood some interesting practice I can use in my future projects - (specifically that counter). I know a lot of stuff but putting my hands into this project and actually do it, practice will beat any time what I read in the past and my general knowledge. Im happy I made it work. Now I can say more confidently I am more good with logic gates than when I started, for sure.

 

[_q12x_]

Also mister @marconi , did you made that gray code circuit already? Do you have a movie to present it? Also Im curious on your approach/ design. How did you use it or at least assemble it?

 

[_q12x_]

So mission accomplished -
I am discompleting all the breadboards and put back all the IC's today.
So no way to get back now. I will wait 2h before doing it, until your answer here.
After that I will do it.

 

[marconi]

A simple way is to convert a 4 bit binary code into a 4 bit Gray code using combinational logic. See video above.

The three logic gates are EXOR. A Two input EXOR gate can be made from NAND gates.

The XOR gate is built from four NAND gates like this:

The XOR symbol is

 

[_q12x_]

So... it is ok to dismantle the led matrix counting mini computer from the breadboards.
Ok.

 

[marconi]

If you wanted an even simpler way you could use a 4 bit counter and the eeprom and construct a ‘look up table’.

 

[marconi]

Also mister @marconi , did you made that gray code circuit already? Do you have a movie to present it? Also Im curious on your approach/ design. How did you use it or at least assemble it?

I used 4 jk flip flops each connected as a type T (toggle). I made some combinational logic but could have used a look up table to cause each flip flop to change state or not depending on the current state - ‘ if then otherwise‘ type logic. This makes what is called a 'finite state machine'.

 

[_q12x_]

Project finished.
I disassembled everything from the breadboards.
Target was reached.
Thank you all. What an adventure, right? Haha.