MCes wrote:5.25V is the limit of the TTL chip, not of the board: feed the C64 Vcc line to read 5,25V on pin 14-28 of plankton an then read the Vcc on CPLD.
There are 3 different types of ICs on the standard breadbin C64; TTL (all 74LSxx), CMOS (DRAM and color SRAM) and NMOS (all 65xx). All 3 have different characteristics.
All memory datasheets that I found declare a "Recommended Operating Conditions" 5V+-10% ( from 4,5V to 5,5V) with 7V of "Absolute Maximum Ratings",so I never run up over 5,25V for TTL or 5,5V for RAMs, as 3,6V for your CPLD....
It's strange that if the C64 is yours one you don't reach at "Absolute Maximum Ratings" but you want stay deep inside of "Recommended Operating Conditions"....
There is only one type on PLAnkton... that's why. Since this IC is still available and in production, I had the luxury of running destructive tests... I believe I already mentioned that.
May be that now I am a little bit malicious, but now we have to wait the evidence of your test
Pics will be appreciated
I am your humble servant... I will deliver, as I did with the photos of the VIC-20 a few weeks ago.
The only unpleasant part of your request is fitting my lab PSU to a hacked C64 PSU so I can adjust the 5V to the desired level. Otherwise, it's all too easy.
No one can do everything. Everyone can do something.