Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!pilchuck!dataio!fnx!del
From: del@fnx.UUCP (Dag Erik Lindberg)
Newsgroups: comp.os.cpm
Subject: Re: UNIX Z80/CPM EMULATOR (progress report)
Message-ID: <816@fnx.UUCP>
Date: 9 Dec 90 05:30:24 GMT
References: <9012010454.AA22006@yoda.eecs.wsu.edu>
Reply-To: del@fnx.UUCP (Dag Erik Lindberg)
Organization: I/Ovations    Kirkland, WA
Lines: 26

In article <9012010454.AA22006@yoda.eecs.wsu.edu> dwatola@YODA.EECS.WSU.EDU writes:
>
>apparently off).  i only made a few compromises, the main one being that

I am impressed with your effort, and look forward to seeing what you have
done.

>i ditched all BCD support.  as far as i am concerned, it is a waste of time
>since i never use it.  ditching the half-carry flag emulation sped up the

This is unfortunate, and will break more programs than you might suspect.
The following seemingly innocuous code is a fairly common and extremely
space efficient hack to convert a 4 bit binary number into ASCII ("0"-"F")
representation of the hex value:

	add	a,090H		; Set overflow character
	daa
	adc	a,040H		; Add with ASCII offset
	daa

Notice that it uses only 6 bytes, but includes the 'daa' (Decimal Adjust
Accumulator), which is a BCD opcode.

-- 
del AKA Erik Lindberg                             uunet!pilchuck!fnx!del
                          Who is John Galt?