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Pushing the 3.3V<->5V envelope
rea5245:
I want to interface a 6502 to a modern microcontroller, a PIC32MZ. The PIC32 has some 5V tolerant pins, but not enough. Instead of using a level shifter, my idea is to run the PIC32 at 3.6V (which is allowed by spec) and wire it directly to the 6502. I've measured some voltages on the 6502's data and address lines and they seem to go no higher than 3.5 or 3.6V. Meanwhile, the "absolute maximums" spec for the PIC32 says that input pins can handle Vdd+0.3V.
It sounds like I can get away with this. Am I playing with fire, or am I OK?
Thanks,
Bob
Chris_Walch:
You could use a 3.3V variant of the 6502
https://www.westerndesigncenter.com/wdc/documentation/w65c02s.pdf
rea5245:
This is vintage hardware. It already has a 5V 6502 and lots of 5V support chips.
- Bob
Chris_Walch:
Outputing signals from the PIC to the 6502 should work as the threshold seems to be around 2.4V.
The output stages of the CMOS 6502 variants pull the signals quite close to the supply voltage.
So connecting an 5V output of the 6502 to the PIC input might cause problems.
james_s:
I'd probably use some resistors in series with the lines, I've used that technique before as a quick hack and it worked fine.
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