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PostPosted: Thu Nov 04, 2021 8:33 pm 
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I'm planning in doing some expermiments by using my C64 (as I call it, "cost reduced") chips and a couple of WDC's 6502 and 65816 chips I have.

But before breaking something and already having in mind all the voltage stuff, I'd like to know if I can interface directly the chips between them, even being from different xMOS types (NMOS, HMOS, CMOS).

Or should I put extra components between them?

Thanks all.


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PostPosted: Thu Nov 04, 2021 8:59 pm 
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As long as you stay with 5 volts and don't get your polarities crossed, you shouldn't risk much by experimenting with different configurations. Many combinations should work under normal circumstances, even if the ranges of the operating specs. indicate possible failure.

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PostPosted: Thu Nov 04, 2021 9:02 pm 
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Thank you very much.


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PostPosted: Thu Nov 04, 2021 9:37 pm 
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You need to check the data sheets for the chips you intend to use. Some CMOS devices expect high inputs to be >70% of Vcc (=3.5V) and low inputs to be <30% of Vcc (=1.5V) - in fact if you look at the data sheet for the W65C22S it says 80% VCC for logic 1, 20% for logic 0. NMOS is TTL level (low is <0.8V, high > 2V) and the outputs are usually only specified to be 2.4V for logic 1. CMOS output driving NMOS input should be fine. NMOS output driving CMOS input can be problematic.


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PostPosted: Thu Nov 04, 2021 11:12 pm 
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See Jeff's excellent (as usual) head post in the topic "TTL Compatible... NOT! ( WDC )." See also the links at the bottom of the 74xx logic-families page of the 6502 primer, at http://wilsonminesco.com/6502primer/LogicFamilies.html .

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PostPosted: Fri Nov 05, 2021 6:22 pm 
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Thank you very much. I think I'll have to learn more about basic electronics before going into this.


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