MAX V 5 volt compatible...good for retro stuff?

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MAX V 5 volt compatible...good for retro stuff?

Post by getafixx » Wed Nov 29, 2017 9:08 pm

According to the datasheet (page 89) it says that thanks to the "Multi-Volt" tech inside, this CPLD is fully compatible with 5V TTL logic without the need for external resistors. It says for CMOS it would need pullups, though.

So, my question is do these old 5V game consoles all run at TTL levels, or is there a list somewhere showing what runs on what logic?

Link to sheet is here

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Re: MAX V 5 volt compatible...good for retro stuff?

Post by lidnariq » Wed Nov 29, 2017 11:20 pm

The MAX V devices still have an overvoltage protection diode on its pins to the VCCIO supply. It is not suitable for being driven directly by a 5V signal:
(5) MAX V devices can be 5.0-V tolerant with the use of an external resistor and the internal I/O clamp diode on the 5M1270Z and 5M2210Z devices.
Use an external clamp diode if the internal clamp diode is not available.
The big difference here is that the overvoltage protection diodes are rated for continuous use, in comparison to "plain" 3V parts.

VCCIO also has an absolute maximum rating of 4.6V, so you can probably operate it at VCCIO of 4.1V or so and get away with very small current limiters for the overvoltage protection diodes.

edit: To belatedly answer the other question: we know that the SNES is a 5V CMOS device; things running at 3.3V are documented to fail/glitch rarely (whereas if the voltages were truly 5VTTL they'd be fine with 3.3VCMOS levels). I don't really know about other consoles.

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