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.
eslapion wrote: ↑Thu Jul 09, 2020 12:13 am
MCes wrote: ↑Thu Jul 09, 2020 12:09 am
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:
MCes wrote: ↑Fri Jun 26, 2020 2:27 pm
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.
eslapion wrote: ↑Wed Jul 01, 2020 8:57 am
(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
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." (Albert Einstein)