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From: foperator@tekno.chalmers.se (Daniel Berglund)
Newsgroups: sci.electronics
Subject: NMOS/TTL driving CMOS?
Message-ID: <811@tekno.chalmers.se>
Date: 7 Jun 89 19:24:17 GMT
Organization: Chalmers Univ. of Technology, Gothenburg, Sweden
Lines: 21

Is it possible for an NMOS device (in this case, a 68000) to utilize CMOS
(74HCxx) interface circuits? The data sheets say that Voh from the 68000 is 
_at least_ 2.4 V (and at most Vcc), but an HC device wants at least 3.15 V to be
happy (@Vcc=5V). 

Can I safely assume that the 68000 lines, if connected to "only a few" HC
inputs (and no power-eating LS-TTLs), will be able to pull the voltage level up
to a value acceptable by the HC circuits? 

Or do I have to resort to HCT devices? I don't like the idea of adding another
dozen of chips just for the sake of level-shifting. It would be much easier if
those HCT devices came in all flavours and not just in the
buffer-and-latch-related ones.. (actually, they seem to be _fabricated_ but 
not _sold_, at least not by the dealers I usually use) 

Similary, would an LS - or better ALS - device pull up to CMOS levels when
connected to only one or two HC inputs? 

-- 
Daniel Berglund       (foperator@tekno.chalmers.se, BITNET: FOP@SECTHF51)
Chalmers University of Technology, G|teborg, Sweden