Search found 1557 matches

by Andy Rea
Tue Feb 25, 2020 7:46 pm
Forum: Emulators
Topic: A new ZX81 Emulator
Replies: 9
Views: 1803

Re: A new ZX81 Emulator

When we reach the RET of routine keyboard HL will be something of the following 1 - 2 - 3 - 4 - 5 -> register L = F7 0 - 9 - 8 - 7 - 6 -> register L = EF Q - W - E - R - T -> register L = FB P - O - I - U - Y -> register L = DF A - S - D - F - G -> register L = FD N/L- L - K - J - H -> register L = ...
by Andy Rea
Sun Oct 13, 2019 4:09 pm
Forum: Welcome Area
Topic: Hello from Nottingham, UK.
Replies: 21
Views: 4167

Re: Hello from Nottingham, UK.

Welcome to the Forum, Lots of love for the humble machine. you can really do alot with it.

any questions just ask away.

Regard Andy
by Andy Rea
Mon Oct 07, 2019 1:37 pm
Forum: Hardware
Topic: Mystery 330 ohm resistor connected to X1
Replies: 4
Views: 1493

Re: Mystery 330 ohm resistor connected to X1

I've seen similar on zx81 isue 3 boards with red solder mask but in my case they were 1K resistors

Andy
by Andy Rea
Tue Oct 01, 2019 2:21 pm
Forum: Hardware
Topic: ZXPand vs ZXPand+ ?
Replies: 2
Views: 1381

Re: ZXPand vs ZXPand+ ?

put the sd in after powering on and see if it is recognised do a CAT
by Andy Rea
Mon Sep 30, 2019 9:55 pm
Forum: Development
Topic: DOOM on ZX81?!
Replies: 3
Views: 1790

Re: DOOM on ZX81?!

awesome that preview looks really smooth, will download and try on real hardware... BOBS played with ray traced texture mapping in lo-res a long time ago... https://www.sinclairzxworld.com/viewtopic.php?f=4&t=548&p=4951&hilit=3d+rendering#p4951 the facebook video link https://www.facebook.com/bobs.s...
by Andy Rea
Mon Sep 30, 2019 9:50 pm
Forum: Hardware
Topic: Re-enable ZXpand after CONFIG "X"
Replies: 6
Views: 1921

Re: Re-enable ZXpand after CONFIG "X"

Nice Trick, Thanks for sharing...

Andy
by Andy Rea
Fri Sep 27, 2019 11:45 am
Forum: Development
Topic: Problem with TASM 3.2
Replies: 10
Views: 2584

Re: Problem with TASM 3.2

yes JR 4 bits lol nope..

JR and index offsets both 8bit SIGNED
by Andy Rea
Fri Sep 27, 2019 11:29 am
Forum: Development
Topic: Problem with TASM 3.2
Replies: 10
Views: 2584

Re: Problem with TASM 3.2

quoted instead of edit :( sorry
by Andy Rea
Fri Sep 27, 2019 11:28 am
Forum: Development
Topic: Problem with TASM 3.2
Replies: 10
Views: 2584

Re: Problem with TASM 3.2

haha your right the IX and IY registers can't be negative but for example say they are holding the value $0000 and you add a negative offset it will roll round to $ffff for -1 $fffe for -2 $fffd fro -3 and so on... btw LD IY,-20000 ; is perfectly valid and results in the following bytes DD 21 E0 B1 ...
by Andy Rea
Fri Sep 27, 2019 9:55 am
Forum: Development
Topic: Problem with TASM 3.2
Replies: 10
Views: 2584

Re: Problem with TASM 3.2

when using the index registers the offset byte is signed so -128 to +127 is the maximum range allowed.

same as relative jumps.

tasm allows you to enter negative numbers.

regards Andy