csquared3 at tx.rr.com
Sat Jan 30 22:19:04 CST 2010
Tony Duell wrote:
>> When I moved from the 6800 to the 6809 (in assembly language - *many*
>> years ago) I was sort of astounded and at the same time very pleased by
>> the way many of the little subroutines I had written for the 6800 became
>> one instruction in the 6809. I think it will always be my favorite
>> 8-bit CPU. My only annoyance at the time was the fact that there was no
> I was a confirmed Z80 hacker until I bought a CoCo 2 in a clearout sale.
> And after reading the 6809 data sheet I fell in love with that chip.
>> way for the software to reset the companion UART chip, whose number I've
>> completely forgotten by now. 6821 maybe???
> The 6821 is the parallel chip (2 16 bit perts). The serial chip, commonly
> called te ACIA is the 6850. It needs an external baud rate generator.
> There was also the 6852 synchronous serial chip and the 6854 which did
> some other flavour of synchonous comms and was used in the Acorn Econet
> Of course you could also use 6502-series I/O chips on a 6809 (and vice
> versa), the buses are essentially the sane,. The 6522 VIA is a nicer
> parallel chip (with counter/timers, a shift register, etc). The 6551 is a
> serial chip with a built-in baud rate generator.
Many thanks to you and Henk for reminding me what the Motorola "UART"
chips were called/numbered. All this discussion is making me want a
CoCo unfortunately. Never had one when they were "new" but always
thought they would be a lot of fun - maybe a garage sale will turn one
up some day. Just what I don't need of course - yet another project or
piece of hardware.
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