Charlie's Red Ant - a ROM instruction that reads throughout memory

Discussion about ZX80 / ZX81 Software
User avatar
PokeMon
Posts: 2264
Joined: Sat Sep 17, 2011 6:48 pm

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by PokeMon »

Andy Rea wrote: Sun Sep 10, 2017 10:35 pm since as hl is stored after this instruction
A bit of all, H is (re)stored after this instruction. :mrgreen:
olofsen
Posts: 189
Joined: Wed Jan 08, 2014 12:29 pm

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by olofsen »

Thinking about a "claire.p" that shows a "thumbs up" path in the Live Memory View... ;)
User avatar
zsolt
Posts: 214
Joined: Wed Apr 20, 2011 11:43 am
Location: Fót, Hungary

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by zsolt »

Hi,
dr beep wrote: Sun Sep 10, 2017 10:22 pm
sirmorris wrote: Sun Sep 10, 2017 6:59 pm Also,

Code: Select all

L0237:  LD      B,(HL)          ; (7) Note. Harmless Nonsensical Timing weight.
Is exactly it :D
So the fix should be LD H, (HL)
Why is this the solution? :o This is same memory reading.
Zsolt
ZX81 (8K), ENTERPRISE 128, [ZX SPECTRUM (48K,+,+128K,+2,+2A), TS1000, TS1500, TS2068, Cambridge Z88, PRIMO A64 (red)]
dr beep
Posts: 2060
Joined: Thu Jun 16, 2011 8:35 am
Location: Boxmeer

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by dr beep »

zsolt wrote: Tue Sep 12, 2017 4:58 pm Hi,
dr beep wrote: Sun Sep 10, 2017 10:22 pm
sirmorris wrote: Sun Sep 10, 2017 6:59 pm Also,

Code: Select all

L0237:  LD      B,(HL)          ; (7) Note. Harmless Nonsensical Timing weight.
Is exactly it :D
So the fix should be LD H, (HL)
Why is this the solution? :o This is same memory reading.
Zsolt
The timing must be the same, but B gets a value that is not allowed.
CP (HL) might work too, but it does effect the Z-flag where LD H,(HL) has no effect on flags but still use 7 tstates in 1 command and 1 byte.
User avatar
Andy Rea
Posts: 1606
Joined: Fri May 09, 2008 2:48 pm
Location: Planet Earth
Contact:

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by Andy Rea »

Just for fun.... :lol:
REDSINC.P
(2.11 KiB) Downloaded 251 times
regards Andy .
what's that Smell.... smells like fresh flux and solder fumes...
olofsen
Posts: 189
Joined: Wed Jan 08, 2014 12:29 pm

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by olofsen »

Thanks :) I think I'll have it running all night on real hardware - it works quite well even with monitor switched off and eyes closed ;)
User avatar
Andy Rea
Posts: 1606
Joined: Fri May 09, 2008 2:48 pm
Location: Planet Earth
Contact:

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by Andy Rea »

did i forget to mention it works very well on eightyone V1.7 :mrgreen: :mrgreen: :mrgreen:
what's that Smell.... smells like fresh flux and solder fumes...
User avatar
zsolt
Posts: 214
Joined: Wed Apr 20, 2011 11:43 am
Location: Fót, Hungary

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by zsolt »

dr beep wrote: Tue Sep 12, 2017 6:25 pm The timing must be the same, but B gets a value that is not allowed.
OK, it is time-correct, but does not solve the original "problem":
sirmorris wrote: * Yes, the ZX81 appears to have a pet - a restless red 'ant' (escaped from the classic game?) which relentlessly patrols RAM from the end to the start. It's (most likely) a read instruction in the display routine.
(if it is a real problem)

Andy, what should I see there?
ZX81 (8K), ENTERPRISE 128, [ZX SPECTRUM (48K,+,+128K,+2,+2A), TS1000, TS1500, TS2068, Cambridge Z88, PRIMO A64 (red)]
User avatar
1024MAK
Posts: 5101
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by 1024MAK »

Well, it's been in the ROM since 1981...

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
sirmorris
Posts: 2811
Joined: Thu May 08, 2008 5:45 pm

Re: Charlie's Red Ant - a ROM instruction that reads throughout memory

Post by sirmorris »

It's not a problem! It's a pet!
Post Reply