> Can't you just read back the register value?  Some bits might not have
> identical meanings in read and write operations for a same register,
> but I thought most of them could be read back...  Well, I may be wrong
> as it was a loooooong time ago when I actually wrote a Z8530 driver
> for OS-9/68k...
> 
> I'll dig up my Z8530 data sheet if you want (I think I still have it
> somewhere).
> 
> Cheers,
> 
> ken n.
> 

I just looked at my data sheets (I'd be happy to send anyone a copy that
needs it).  There are two distinct register sets for each channel.  One is
_write only_ the other is _read only_.  The only over lap is the baud rate
generator constants, and interrupt vectors.  From what I can see the only
way to keep track of control bits is to shadow them in memory some where.
(What is so difficult about designing a SCC?  This is not the only SCC
I've seen with such a lousy programmer interface. :)

Kevin
kevin@spef.syr.ge.com