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From: hugh@hcrvx1.UUCP (Hugh Redelmeier)
Newsgroups: net.micro.atari16
Subject: CP/M-80 Z80 Emulator Bug
Message-ID: <1429@hcrvx1.UUCP>
Date: Mon, 10-Nov-86 18:01:24 EST
Article-I.D.: hcrvx1.1429
Posted: Mon Nov 10 18:01:24 1986
Date-Received: Tue, 11-Nov-86 00:33:45 EST
Organization: Human Computing Resources, Toronto
Lines: 52

I have just spent some time putting up the CP/M-80 emulator on my
1040ST.  I have found the emulator seems quite well done.  But there
are some problems with it.

In the Z80, there are two flags for purposes of BCD arithmetic:  the
H flag is for recording "half-carry" and the N flag is for recording
whether the last operation was an add or a subtract.  An AND
instruction sets both N and H flags.  Similarly, an OR instruction
clears both.  (In the 8080, there is no N flag, and both the AND and
OR instructions clear H.)

In the emulator, the AND and OR instructions seem to leave the N and
H flags alone.  So it does not match the Z80, or even the 8080.
Although this seems unimportant, I only discovered it because it
caused the program that I was porting to fail.


The emulator seems to support only floppy drives.  I could not get
it to use a RAM disk (I use the Intersect RAM disk at the moment).
Since the disks it uses must have a CP/M file system, I don't wish
to try my hard disk.  Even on a floppy, it only supports a single
side!  This makes the emulator much less useful on a system with
only one floppy drive.

The make_cpm command (to start the bootstrapping process of creating
the first CP/M disk) prompts at the start.  DO NOT put the blank
disk in at this point.  It needs to fetch a file from the TOS disk
(which must be on a floppy, I think).  Put the blank disk in at the
second prompt.  If you do put in a blank disk the first time, you
will not get a diagnostic.  The machine will just fall asleep for a
minute and then return to the desktop.

I sure wish that the TOSCPM and CPMTOS commands (for transferring
files between TOS and CP/M file systems) would take ambiguous file
names.  As it is, a command must be issued for every file
transferred.

I don't see a way to change what terminal the console emulates.  My
ST is replacing a Kaypro II.  But since the Kaypro emulates an ADM-3
(more or less) and the ST emulates a VT52 (more or less), I cannot
trivially move my programs.  (Legality is another problem, but I am
not talking about copyrighted programs.)

The emulator is not quite good enough to be useful to me.  Just a
few enhancements could change this.

Now that this program is free, I wonder how much support will be
provided by Atari or the original developer (a company in West
Germany).

Hugh Redelmeier (416) 922-1937
utzoo!hcr!hugh