Search found 189 matches

by olofsen
Wed Jul 21, 2021 7:09 pm
Forum: Development
Topic: ZXText2P for ZX80??
Replies: 4
Views: 1791

Re: ZXText2P for ZX80??

Attached is the source of a relatively untested port of a relatively recent, so not the latest, zxtext2p:
zxtext2o.c
(26.1 KiB) Downloaded 183 times
by olofsen
Wed May 26, 2021 7:18 pm
Forum: ZX BASIC
Topic: Why "C"?
Replies: 4
Views: 2439

Re: Why "C"?

Perhaps it is best to call INKEY$ once

Code: Select all

LET I$ = INKEY$
and test only I$ in the subsequent code.
by olofsen
Tue Jul 28, 2020 8:39 pm
Forum: Hardware
Topic: OUT & vertical sync timing
Replies: 5
Views: 2975

Re: OUT & vertical sync timing

by olofsen
Sat Jul 25, 2020 7:42 pm
Forum: Development
Topic: What's the deal with EXX
Replies: 2
Views: 6200

Re: What's the deal with EXX

HL' is used by the calculator as a return address. So using EXXs may cause a crash when using USR, which is a calculator function. With CLS, HL is probably changed, and therefore HL'...
by olofsen
Tue Jun 16, 2020 9:02 am
Forum: Software
Topic: ZigZags by Noice, colorized
Replies: 2
Views: 9728

Re: ZigZags by Noice, colorized

It seems NXTLIN points to a line at 403C where there is a USR 16458 (8F 00 94 00 00). The ZigZags look very good with colours! :)
by olofsen
Fri Jun 12, 2020 7:45 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 20091

Re: ZX81 interrupts with z88dk, how to install an ISR ?

So the address may be located by disassembling the P file and looking for the end of the alternative DISPLAY-3: 4167 ed44 neg 4169 3c inc a 416a 08 ex af,af' 416b d3fe out (0feh),a 416d 2a8b41 ld hl,(418bh) 4170 23 inc hl 4171 228b41 ld (418bh),hl 4174 7c ld a,h 4175 b5 or l 4176 c27d41 jp nz,417dh ...
by olofsen
Thu Jun 11, 2020 6:49 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 20091

Re: ZX81 interrupts with z88dk, how to install an ISR ?

Just a note that the clock available here https://sinclairzxworld.com/viewtopic.php?p=17265#p17265 hooks up an ISR, but I don't remember all details... The address of a C function (although consisting of assembly code) is "poked" to the startup code of the ISR that z88dk installed, at 0x41b4.The sou...
by olofsen
Tue May 19, 2020 7:03 pm
Forum: Development
Topic: New ToddyForth with built-in editor & block storage (Was: TasWord as editor for ToddyForth)
Replies: 31
Views: 23257

Re: TasWord as editor for ToddyForth

Great article :) Trying it I got stuck before step 1 ;) of the workflow though, combining TasWord with your patches... Could you perhaps show how to use SIMDOS2 for this purpose?
by olofsen
Thu Jan 23, 2020 7:52 am
Forum: Emulators
Topic: Emulating musical tones using cassette out - help!
Replies: 7
Views: 9180

Re: Emulating musical tones using cassette out - help!

Indeed, the code is used only for the first value in the sound buffer after an IN or OUT. The "newpos" and "subpos" variables are calculated like an integer division and a remainder. So I guess the "subpos" variable smoothes things a bit by not taking the initial value itself, but taking into accoun...
by olofsen
Mon Jan 20, 2020 11:52 pm
Forum: Emulators
Topic: Emulating musical tones using cassette out - help!
Replies: 7
Views: 9180

Re: Emulating musical tones using cassette out - help!

Some quick thoughts: Indeed with IN the signal should go low, and with OUT high, which would suggest the sound_beeper argument in sz81 is reversed. And indeed INs (with an even port number) are prevented to cause VSYNCs when a program is running, which is with NMIs in SLOW mode. The IN/OUT works as ...