AT28C16 EEPROM learning experiments

_q12x_ · Sep 16, 2022

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_ · Sep 21, 2022

I told you, this 7493 counter needs something 'special' on its R01. As you remember from my previeous videos, if I give it a direct metal wire link to other pins, it is working without any issues. Im thinking maybe the voltage is too low, being absorbed by the AND gate and not enough to drive the pin of the counter....Im thinking a transistor to buffer up the voltage?

_q12x_ · Sep 21, 2022

adding a transistor to the AND Gate
-now counting to 4 and resetting - like the first 4081

_q12x_ · Sep 21, 2022

I put the osciloscope on the 7493
R02 does not get high at all. Only R01 and CKB.
What is the role or what is the mechanism of R01 and R02?

[ElectriciansForums.net] AT28C16 EEPROM learning experiments

marconi · Sep 21, 2022

Please see video of your circuit slightly modified counting states 0 to 6 and then resetting and repeating. It is important that Ro1 and Ro2 go high and low at exactly the same time so that all four ff are reset to 0 at the same time too.

You may find two 2 input CMOS AND gates or the 3 input diode circuit will do what my 4 NANDS do below - to AND together Qa, Qb and Qc.

Note well please that the far right gate is a NAND - I missed off its small circle on the output.

_q12x_ · Sep 21, 2022

marconi said:
counting states 0 to 6 and then resetting and repeating

yes, indeed it is counting to 7, 6 visible but 7 resets to 0 but is still a 7.
if you start counting from 0 to 6, you get 7 counts.

marconi said:
Note well please that the far right gate is a NAND - I missed off its small circle on the output.

ok so 4 NAND Gates. Got it.
Glad that you made it work !!!! I was out of any ideas.
Will see if it will work on mine now.
Let me try it quickly in the simulator first to confirm it.
then I will get into real thing.

_q12x_ · Sep 21, 2022

Ive inverted your circuit to fit my circuit:

And I simulated it already and, miracle, it works !!! (in the simulation)

Now I will try it in reality.

_q12x_ · Sep 21, 2022

YES, mister @marconi it works in reality as well.
Really, Congratulations !
I am making the movie right now and post it very soon !
What a ride... Im very happy !
Thank you.

_q12x_ · Sep 21, 2022

While at this stage... can you explain to me how you think? How is your logic about these logic gates? How did you managed to come to this circuit? The logic before making the circuit ! What you were thinking?

_q12x_ · Sep 21, 2022

Here is the video about your success mister @marconi !

marconi · Sep 22, 2022

_q12x_ said:
While at this stage... can you explain to me how you think? How is your logic about these logic gates? How did you managed to come to this circuit? The logic before making the circuit ! What you were thinking?

The 4 Nand gates are used to make two 2 input And gates. If you study the circuit you can see how first Qa and Qb are combined by And. The output of this And is an input to the second And gate along with Qc. The second and gate produces a logic 1 when Qa, Qb and Qc are all logic 1 to send a reset pulse to R1 and R2.

Why it matters to connect R1 and R2 together is because we have to ensure that the reset inputs go to logic 1 and logic 0 at exactly the same time. There is actually rather more technical detail but forgive me for saying it would not be easily understood by you now. Just to mention that propagation delays, assertion and de-assertion durations for the reset signals, reset recovery times, meta-stable states of the flip flops and the timing of state changes including of the clocks ClkA and ClkB come into play. Things happen very quickly inside the 7493 but not instantaneously - there is sequencing of internal state changes which take a finite time to complete and are ensured by the modifications I have shown you.

marconi · Sep 22, 2022

So next you are working on the 74138 circuitry?

_q12x_ · Sep 22, 2022

marconi said:
Why it matters to connect R1 and R2 together is because we have to ensure that the reset inputs go to logic 1 and logic 0 at exactly the same time.

From that entire explanation, what is trully important to me and actually explains a behaviour, a cause and effect if you will, is ONLY this proposition. Try to concentrate on this kind of explanation at least with me. To advance faster and further !!! Its our only goal, right?