On 9/5/2022 8:51 AM, Rainer Buchty wrote: > On Sun, 4 Sep 2022, Gerrit Heitsch wrote: > >> But would that also cover the illegal Opcodes correctly? From what I >> understand, those are side effects of the NMOS implementation. > > Were they? I always considered them to be a side-effect of the > internal decoder matrix which did not specifically "NOP" the unused > opcodes (which IIRC was done with the CMOS versions), but just bluntly > decoded the individual parts of the opcode, generating corresponding > enable signals. > > So stuff happened like e.g. loading the accumulator, but also throwing > the X register onto the internal data bus. As I recall, a few incomplete decodes enabled two things to bump data onto a bus, which would then boil down to NMOS behavior with 2 outputs pushing electrons to the input. Jim > > Rainer > > -- Jim Brain brain_at_jbrain.com www.jbrain.comReceived on 2022-09-05 19:03:44
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