Exactly how NOT to make a multicart for the C64

[eslapion]

pending questions:
--The list of who had it's VIC 20 C64 connector damaged by the HASL cartridge finishing (or equivalent evidences).

This thread was about a C64 cartridge which uses HASL, why would you want VIC-20 pics ?

--The pics of the gerber view of SARUMAN-TED V1.2

Why do you want that ? They were faulty. I trashed them.

I learned from you that the C16 and Plus/4 uses Early Write Cycle with DRAM.

With the levels of the C64 chips, the Australian chips will also work, of course I would have used HCT to maintain greater immunity from noise, but it is a design choice that remains within the operating limits of the chips themselves.

Strictly, absolutely nothing to do with noise immunity. You get this out of your hat.

The correct answer here: https://www.onsemi.com/pub/Collateral/AN-368.pdf.pdf

Another thing you say a lot of things about but understand nothing.

[MCes]

I learned from you that C16 PLUS4 cpu/TED sockets have very poor quality,
and I found interesting some threads of yours about testing on C64 boards of different ages.

pending questions:
--The list of who had it's VIC 20 C64 connector damaged by the HASL cartridge finishing (or equivalent evidences).

This thread was about a C64 cartridge which uses HASL, why would you want VIC-20 pics ?

My google translator is informing me that also you don't think that "HASL finished" cartridges are dangerous for the VIC20 connector.


I already told:

I also believe that it is a good design rule to use HCT on these machines, as it is a good design rule not to boost the chip power supplies, as you do, even beyond the maximum allowed by the manufacturer data.
With the levels of the C64 chips, the Australian chips will also work, of course I would have used HCT to maintain greater immunity from noise, but it is a design choice that remains within the operating limits of the chips themselves.

Into the document that you posted for explain why my concepts are wrong it is possible to find exactly my concepts:
"It should be noted that in an actual application the TTL output will pull-up probably to about VCC minus 2 diode voltages,
and HC will accept voltages as low as 3V as a valid one level so that in almost all cases there is no problem driving HC with TTL."

TTL Voh min=2.4V is guaranteed for a specific current, but if a TTL will be loaded only with C-MOS inputs the current will be near zero and the TTL Voh will be described by its internal scheme: a pull-up resistor that polarize 2 cascaded transistor: Vcc-2xVbe=3.6V approx, and this is the case of the "Australian" circuit.
Into "The C64 PLA Dissected" Skoe identify as 1.3V the Vcc-Vo drop of unloaded Commodore N-Mos output pin, as an TTL output unloaded,
so also the N-MOS outputs that feed the Australian cartridge will be well recognized (but with a reduced noise margin..)

on Chapter "NOISE MARGIN TRADEOFFS WITH HCT" it can be seen that also Farchild indicate the HC Vth of 2.5V like as the reference for calculate the noise immunity, and it's clear that the margin decrease if the input is feeded by reduced input level that is sufficient but not too far by the Vth=2,5V.

(Skoe) is the one who indicated on German forums a properly designed PLA replacement for the C64 must signal at 3.7V or MORE.

It's interesting, could you post this link?
thanks

[eslapion]

It's interesting, could you post this link?

I posted it on Amibay, you responded with flaming posts and it got deleted along with your posts.

Memories are short. Dynamic and requires refreshing, I suppose.

https://www.forum64.de/index.php?thread ... /&pageNo=2

TTL Voh min=2.4V is guaranteed for a specific current, but if a TTL will be loaded only with C-MOS inputs

Like every VIC-20 and C64 internal signal is loaded ONLY with the CMOS ICs you would attach to them.

In the case here, the multicart uses an octal D Flip-flop to select which game is played. This IC is tied to the 8 bit databus of the C64 and there is easily a dozen NMOS and TTL ICs tied to that bus. Ergo, using a 74HC273 is a MISTAKE !

On 5V CMOS ICs, Vth=Vcc x 0.5 -> Vth=5V x 0.5=2.5V THAT'S TOO HIGH !!

[Noizer]

[Gyro Gearloose]

[eslapion]

Well, more like...

Meep meep!

[groepaz]

Looks like we didnt reach the peak of the discussion yet afterall

[Robbie]

Sorry to resurrect this thread, but I've only just discovered it and wanted to congratulate all involved.

It reminds me of a conversation I once overhead about the Duckworth-Lewis Method for determining who wins the cricket when it starts raining: ( https://en.wikipedia.org/wiki/Duckworth ... ern_method ). Everyone knows that the Duckworth-Lewis Method was only invented to give people something to argue about while waiting for it to stop raining.

[orion70]

Well, the rain has stopped, at least here in Denial, so please leave this thread as it is