Search found 4648 matches

by Mike
Wed Jan 09, 2013 5:18 pm
Forum: Programming
Topic: ML noob
Replies: 12
Views: 1464

FD22 wrote:Might be an idea to include a note as to which assembler / language-extension you need to build this, as it's certainly not DASM... :wink:
It's the inline assembler of HI BASIC, an implementation of BBC BASIC running on the BBC Micro expansion unit.
by Mike
Wed Jan 09, 2013 3:51 pm
Forum: Programming
Topic: ML noob
Replies: 12
Views: 1464

Applying more pressure we get this one below (download meminfo.prg ): It's already small enough (89 bytes) that it can be loaded to 673 instead, so it also works with a tape drive. I added a blankspace between ':' and '$', the original savings were another 9 (84 versus 93) bytes. REM>MemInfoSrc DIM ...
by Mike
Tue Jan 08, 2013 11:50 am
Forum: Programming
Topic: ML noob
Replies: 12
Views: 1464

If you use the X register with the indexed ZP address mode, you can do: .3 lda (ZPALO),y TAX LDA $00,X jsr PRTBYTE iny cpy #5 bcc .3 Instead of the X register, the outer loop then uses a free ZP address to count down: [...] ZPROW EQU $fd [...] LDA #PTRCNT ; number of arrow rows STA ZPROW .1 [...] DE...
by Mike
Sun Jan 06, 2013 3:28 am
Forum: Emulation and Cross Development
Topic: VICE speed
Replies: 3
Views: 1664

Re: VICE speed

[...] Is the 6502 really that fast [...]? [...] .1 sta ($fb),Y iny bne .1 [...] These three lines are executed most of the time and need 6 (STA(),Y) + 2 (INY) + 3 (executed BNE) = 11 cycles per iteration, for 256 iterations (except for a few missing bytes in the first page) per page, and 14 pages i...
by Mike
Sat Jan 05, 2013 4:54 pm
Forum: Programming
Topic: Interlaced colors - please test & take a photo!
Replies: 10
Views: 2855

lordbubsy wrote:If the photos are too big, i can reduce them to a given width ...
You could replace them with thumbnails+links to the originals, as they make the text in this thread hard to read.
by Mike
Sat Jan 05, 2013 1:38 pm
Forum: Programming
Topic: Protecting screen memory
Replies: 7
Views: 967

Does screen memory always begin at the start of a page? As I already wrote above, the base address of screen memory can only be located at multiples of 512 bytes. The screen editor always places the first editable line at this base address. Any deviation from the standard screen layout, which shoul...
by Mike
Sat Jan 05, 2013 7:30 am
Forum: Programming
Topic: Protecting screen memory
Replies: 7
Views: 967

The only thing that you can do is change the number of rows to 24 and use the first 6 positions of that bottom row. They are addressable at positions 506-511 from start of screen. That only applies, when the screen is located at 7680, as it is for an unexpanded VIC-20 or with +3K RAM expansion. In ...
by Mike
Sat Jan 05, 2013 6:48 am
Forum: Programming
Topic: Protecting screen memory
Replies: 7
Views: 967

Hi, Stromcrow, even if you tell the VIC chip to use another number of rows or columns, the screen editor in the BASIC interpreter still refers to the 22x23 layout, it is hardcoded therein all over the place. :( The VIC chip can locate the start of screen memory only at multiples of 512 bytes, it tak...
by Mike
Thu Jan 03, 2013 3:53 pm
Forum: Programming
Topic: Interlaced colors - please test & take a photo!
Replies: 10
Views: 2855

I agree it's hard to photograph. A tripod and a good choice of aperture are your best friends here. ;) In the meantime, here's this program as an alternative to produce all 28 mixing 'colours' in a systematic way using a checkerboard pattern: ( download ) 10 POKE55,0:POKE56,28:CLR:V=36864 11 POKEV+...
by Mike
Thu Jan 03, 2013 7:13 am
Forum: Programming
Topic: Interlaced colors - please test & take a photo!
Replies: 10
Views: 2855

Re: Interlaced colors - please test & take a photo!

Hi, Aleksi, Have any of you played around with interlaced colors? Some time ago, I did a routine which blended the three global colour registers both between adjacent frames and adjacent lines. It was mainly used to achieve two intermediate grey levels between black and white: ' VIC 20 in Black and ...
by Mike
Tue Jan 01, 2013 7:23 am
Forum: Hardware and Tech
Topic: VIC chip - Dot to TV output timing
Replies: 6
Views: 1356

But I'd imagine that it isn't possible to create two separate pixel areas with border colour between them. [...] would this be a correct assumption? That'd be a fun idea at least to try. For the moment though, my VIC-20 is away at ~600 km distance, so that will have to wait for a few days. OTOH, it...
by Mike
Tue Jan 01, 2013 5:52 am
Forum: Programming
Topic: critique my code
Replies: 6
Views: 881

Hi, I'm surprised those 4 bytes of zero page ($fb-$fe) is all we really get[...] There are some more ZP bytes available, which are normally shared between Tape and RS232 operations. See the thread ' Safe page zero addresses '. Additionally, the ZP addresses 3..6 also seem save to use: even if they'r...
by Mike
Mon Dec 31, 2012 4:30 pm
Forum: Hardware and Tech
Topic: VIC chip - Dot to TV output timing
Replies: 6
Views: 1356

It is possible to write code so it runs in sync to the raster beam, cycle exact. You might take a look at the raster code in the thread ' VIC 20 in Black and White mode ', where (for example) the background/border register of the VIC chip is written several times in a raster to get a border colour i...
by Mike
Mon Dec 31, 2012 3:27 pm
Forum: Hardware and Tech
Topic: VIC chip - Dot to TV output timing
Replies: 6
Views: 1356

Re: VIC chip - Dot to TV output timing

For example, does it have some sort of pixel queue that is always 8 pixels behind? If you look closely at the video signal, you see that VIC already fetches screen and character data in the column before the display area begins, there are two distinctive vertical lines running through the left bord...
by Mike
Fri Dec 28, 2012 2:31 pm
Forum: Programming
Topic: MG Text Edit
Replies: 15
Views: 6549

... who knows? ;) Besides, in the last three years there have been at least another three attempts at writing a similar screen editor for the VIC-20, two of these being described here in Denial: o Some unnamed program by KingTrode and o VWrite 1.0 by BBQedIguana . The third case can be linked to FD2...