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mahjongg2 / ZX81plus38

Mij latest ZX81 clone without ULA built from discrete pin through hole components
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LS vs HC vs HCT #7

Open nateo87 opened 2 years ago

nateo87 commented 2 years ago

When picking through parts to use to build this, I notice that for some of the logic ICs, the LS variant is used, sometimes the HC, and other times the HCT. If I have the LS version of one of these chips, but not the HC as specified in the BOM, could the LS version be used regardless? And could HCT be used for all chips?

mahjongg2 commented 1 year ago

No those types of logic do not work together well, you should use only ONE type of logic, for my copy I went with all 74HCxx logic, but I was reported that using all 74LSxx logic also worked, if you make sure that the crystal oscillator (74HC04) uses CMOS, either a 74HC04, or a 74HCT04. or the crystal oscillator won't work, but my clone should work fine with either all 74HCTxx logic or even 74LSxx logic, with LS logic the computer will just use more energy!