At 11:05 02-02-22 +0200, you wrote: >The NMOS (n-channel metal oxide semiconductor) chips in the Commodore can >actively pull signals down, but not up. The opposite is PMOS, which is >quite rare, I think. The combination of NMOS and PMOS is called CMOS >(complementary metal oxide semiconductor), which can drive signals both up >and down. [...] > >I also noticed that the 33pF capacitors in the crystal circuit are >unnecessary. (How did I find this out? I have run out of SMD caps and >resistors; I only had the five capacitors for the MAX232.) > > Marko To make it clear: NMOS technology use two kinds of N-channel transistors: enhancement mode (normally off) and depletion mode ones (normally on). CMOS technology use enhancement mode N-channel and P-channel (instead of depletion mode N-channel). I haven't heard of PMOS logic chips - but the hole mobility is about 2.5 times less than electron mobility and P-channel transistor should have ~2.5 times wider channel to have the same transconductance as N-channel one. So PMOS gates would simply be bigger... Marko - have you tried to exchange the crystal with a different one ? I'm curious if it's not just an accident, that oscillator runs without capacitors. Once I was doing something with AT-mega, and it didn't work without capacitors. Also didn't work with 100nF one (a guy put one 33pF and one 100nF by a mistake) ;-) Konrad Burylo Message was sent through the cbm-hackers mailing list
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