Date   : Thu, 23 Jul 1992 15:11:00 GMT
From   : cis.ohio-state.edu!zaphod.mps.ohio-state.edu!moe.ksu.ksu.edu!hobbes.physics.uiowa.edu!iowasp.physics.uiowa.edu!syswtr@ucbvax.Berkeley.EDU
Subject: Re: Undocumented Z80 Opcodes

In article <1992Jul23.033020.838@wyvern.twuug.com>, alpha@wyvern.twuug.com
(Joe Wright) writes:
> sage@LL.MIT.EDU (Jay Sage) writes:
> : Willy answered me with:
> : 
> : >> Both the '180 and '280 have expanded instruction sets that make use of
> : >> the so-called un-documented instructions, particularly in the ED-xx
> : >> group...
> : 
> : Thanks for the reply, but I did not completely understand it.  I knew, of
> : course, that the Z180 and Z280 had expanded instruction sets, and I would
> : have guessed that most if not all of the so-called undocumented Z80 opcodes
> : would have been used.  The question is, do none, some, or all of the
> : formerly undocumented codes work on the Z180 and Z280 chips as they do on
> : the Z80? 

As things turn out, the Hitachi '180 traps all unused opcodes.  Undefined 
opcodes generate an interrupt (non-maskable, of course), set the trap bit
in the ITC register, and vector to  logical address zero (for MP/M and
CP/M systems, this will simply end the program).

  Willy


End of INFO-CPM Digest V92 Issue #71
************************************