Parallel port question?

3.36 volts is a legal, and fairly ordinary, TTL high level. True TTL drivers never did pull all the way up to +5.

John

Perhaps so, but 3.36 is still a legal TTL high. Classic TTL parts were usually specified for a min Voh in the 2.5-2.7 sort of range, and typs around 3.4.

Slide rule? How dated! I use an HP-35.

John

My laptop gives almost exactly 3.3 V. I would bet that it's 5 volt tolerant

3.3 volt CMOS.

Jonathan

John

Hello John,

This must be a pretty old system if it has TTL chips in there instead of CMOS. Probably right after the abacus and the slide rule calculator (which I am still using...).

Regards, Joerg

Hello John,

Ok, I also use an HP-11C. But when I have to calculate RC, resonant circuits, filters or stuff like that I sometimes crack out the old slide rule calculator. This speeds up the calcs when I want to stay within a range of already released part values or within a standard series. It does raise eye brows at times. At one client they reminded me that they do have Edison electric light.

Regards, Joerg

voltage

Yes, but 3.3 V CMOS will produce legal TTL levels.

Jonathan

It is probably the design of your motherboard. Probably a 3.3v setup.

Maybe you have a 'retro' chipset that emulates TTL levels ? There isn't a 'toob' in there as well is there ? ;-)

Graham

Noooooooooooooooooooooooooo.......................

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Graham

As John has implied, the spec actually stated that it was to be TTL voltage levels on those pins.

Ken

Yes indeed. I think we've all satisfactorily surrounded the answer from all directions and can go home happy. :-)

Cheers.

Ken