15 Dec
2016
15 Dec
'16
3:07 a.m.
On 12/15/2016 02:12 AM, Ethan Dicks wrote:
On Wed, Dec 14, 2016 at 2:08 AM, Alexis Kotlowy
<thrashbarg at kaput.homeunix.org> wrote:
In the past the LD A,R was used to seed a random number generator, not
the best but for
tiny basics and the like is was enough. IT was used in one app I'd seen
as a cycle
counter as part of a debugger since it increments each M1 (instruction
fetch) cycle.
FYI later Z80 variants like 64180, Z180, Z280 that register was at least
8 bit
incrementing. I've designed around them all.
Allison
On 14/12/2016 09:19, Ethan Dicks wrote:
Thanks for the tip, Alexis. It did run
under ZEMU under Wine on my
Mint laptop, but what an awful interface. My next goal is finding
something less mousy like fixing altairz80.
So far, this loop hangs on all three emulators
I've tried - simh's
altairz80, simcpm010 for AmigaDOS, and EMUZ80 for Raspberry Pi...
Have you tried
running it on ZEMU? (Windows only unfortunately, but
should run under WINE).
http://www.z80.info/z80emu.htm#EMU_CPU_W32 I tried single stepping through it just now and
it looks like it's doing
its job, at least as a possible random number generator.
Yep. No tweaks. It just
ran as expected under ZEMU once I got the
files in there.
I can't find any information on what the MSB
is set to when the
accumulator is loaded with R, and what the Sign flag is set to. The
datasheet says the Sign and Zero flags are changed by the instruction.
If either of these flags are set, the routine enters an infinite loop.
The upper
bit of R can be set or cleared with LD R,A but won't change
state due to counter activity. I checked the program - it only does
LD A,R to read the register. It never sets it.
Thanks again for the tip. Once I get a few more things checked out,
I'll be revealing what this is all about. I think a few people may be
interested, or at least amused.
-ethan