On 9/5/2018 5:11 PM, smf wrote: > > On 05/09/2018 19:40, Jim Brain wrote: >> >> a crystal input is a clock input. It may be imprecise, but most >> datasheets use the same term for both input types. >> > No, a clock input (at least a single phase like is used on the 6551) > is a single pin. A crystal has two pins. Not that it matters, but both an externally generated clock signal and a crystal require 2 connections. The crystal requires two differental connections, while the external clock source required the signal and the reference line (ground). >> > I understand that it works. Just because it works, doesn't mean it was > designed. I have no idea how one would ever prove the design intent. Even if the decap shows no special logic in the clock paths, you would still argue that does not show design intent. I think it is far more likely that*The author wanted to reiterate the point that all standard bps rates were available with just a single crystal. The author felt users would only utilize the more expensive external clock signal if they wanted a nonstandard bps rate, so tailored the text to reflect that (if you want std rates, you'll be using the crystal anyway, since it's cheaper, so I'll only talk about that). * As to why 115200 was not used, I find it highly doubtful that CBM would not know the IC could do 115200. And, even if the IC was not designed to do it, we can both agree Commodore would not care. So, if it worked at all (which we know it did), I feel the simplest argument to fit the facts are that no one cared about 115200 at the time. JimReceived on 2018-09-06 03:00:04
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