Re:Dunfield 6809 Portable
by canadian_tired on Friday February 05, 2021 @01:03PM
(#26039253)
It is really an 8-bit CPU from a bus (external connections) perspective...but internally, there were 16 bit registers (sort of...) Perhaps this was why he made the distinction.
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The 8-bit A and B accumulators could be addressed together as a 16-bit D accumulator. The contents of A and B could be multiplied with the product stored in D. There were also two 16-bit index registers with advanced and versatile addressing modes, X and Y, along with 16-bit user and system stack pointers, U and S.
Re:Dunfield 6809 Portable
by jhallenworld on Friday February 05, 2021 @02:22PM
(#26040144)
It's the link between 8-bit and 16-bit: at least that's what Motorola marketing said, look at the cover of this book:
https://www.amazon.com/MOTOROLA-MC6809E-MICROPROCESSOR-PROGR...
I have a copy of that book near me. For a very long time, Moto would send docs out for the mere asking. Free of charge. I got mine as a high schooler. Didn't use the mail though. Instead, I visited a local Moto office and they handed me the ones I wanted and I got to talk chips with the people there for a while.
For a small town kid interested in all this stuff, that made quite an impression. Instant Moto fan.