Re: second processor on a II:How?

[dempson@actrix.gen.nz (David Empson)]

In article <36vhdi$ah4@maxwell4.ee>, Dan P. Scholnik <dpscholn@mtu.edu> wrote:
> : cares if the 6502 resets when you leave your 6809.  Anyway, your 6809
> : won't tell you when its not using the buses, like a Z80 does (with
> : individual read and write lines, and dynamic refresh lines.)
> 
> 	Actually, the 6809 BA line is high when the processor busses are
> tristated. Plus, they are inactive in the first half cycle like the 6502.
> But I don't really care if the registers are saved. I can do it manually if
> needed.

Including the program counter and stack pointer!  If you don't let the
6502 run at all, _every_ internal register will lose its value.

> : Hmmm...  I would have considered a 68HC11 a much more interesting play
> : thing, but each to his own...
> 
> 	I know a lot more about the 6809 than the HC11, but I'll grant you
> that what I do know about it leads me to agree with you. If I get ahold of
> one, I'll do so. The HC11 is software compatible to a 6809, no?

No.  It is upward compatible from the 6801.  The 6809 is a side branch
of the 6801 family, and is not object code compatible with the 6801 or
68HC11.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand