30 Jan
2010
30 Jan
'10
10:28 a.m.
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
system
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.
-tony