On 29 Nov 2010 at 21:00, Tony Duell wrote:
  Why? 
Well, money for one reason.  A 32-bit microcontroller is much cheaper
than the assemblage of CPU+ROM+RAM+Peripherals and speed-wise will
run rings around the older configuration.  And there are several that
are USB-ready if that floats your boat.
  Not that I would ever use an 8255 for anything, a
worse-designed
 parallel interface chip is hard to imagine!  
I suppose it's because 8255s can still be had easily, although there
are still some Z0853606  CIO chips floating around (much better
IMOHO).
I thought it curious that sometimes even Zilog would stoop to using
Intel silicon.  Didn't the ZDS use 8251 USARTs instead of Z80-SIOs?
--Chuck