Disk loading routine

[Tezz]

Hi all,

 

Does anyone have any advice on coding a good disk loading routine? The routine should enable chain loading and unpacking of individual programs (or sections).

 

Lets say for instance you have written a game or demo to be loaded in from a full disk. First you will want to display a short message "loading, please wait" then display a loading picture or intro then after a keypress load in the actual game/demo.

 

I am unsure of how to specify such a routine so that the memory locations that were used by the previous intro are wiped and are free to use for the actual game/demo.

 

I asume that the loading routine will reside someplace in memory thoughout all parts of the project in a place such as page 6. Then all other locations used can be over written during loading?

 

Any advice or source appreciated. I'm sure that it's childs play for you guys!

[Nukey Shay]

I dunno...disk access is so fast (compared to tape), that a "Please wait" screen is really unneeded. And you can make your own programs autostart just by renaming them to autorun.sys. If you wanted 2 seperate programs (loader and program), you could just name the loading program autorun.sys...and that loader program just has a routine to display the message, load in new values to the hardware disk hander, and do a JMP to the actual program's initialization routine.

 

IIRC, to do the loading, vector $0354-5 holds the address where the next access will be sent to, $0358-9 holds the number of bytes being transferred, and $0352 holds the control value ($07=read, $0b=write). Load X with $10, and JSR to $E456.

Once that's done, you'd just JMP to the program that's now in memory.

[Tezz]

IIRC, to do the loading, vector $0354-5 holds the address where the next access will be sent to, $0358-9 holds the number of bytes being transferred, and $0352 holds the control value ($07=read, $0b=write). Load X with $10, and JSR to $E456.  

Once that's done, you'd just JMP to the program that's now in memory.

Cheers Nukey, got some idea of where to start from now.

[Nukey Shay]

Hang on...there's a problem with the above. It assumes that the file to be read is open

Can't recall how to do that within ML...

[Heaven/TQA]

you have to set the SIO block...it's like

 

open#1,4,0,"d:filename" and there is an equivalent in assembler for that... vector for filename, channel, command etc... i can remember read it in de re atari...

 

a custom SIO discroutine is not so difficult as it might be... of course best is a custom one where you leave 2 pokey channels free for playling music while loading...

[tebe]

good routine (cc65) :

 

unsigned char *filename = "part1.dat";

 

const adr1=0x6010;

const adr2=0x9010;

 

int main(void)

{

FILE* plik = fopen(filename,"rb");

 

puts("Loading... Please Wait");

 

fread((unsigned char *)adr1,8000,1,plik);

fread((unsigned char *)adr2,8000,1,plik);

 

fclose(plik);

}

[Tezz]

tebe good routine (cc65) :

Hmm, don't recognise the format of your code? looks like C?

 

Heaven/TQA open#1,4,0,"d:filename" and there is an equivalent in assembler for that... vector for filename, channel, command etc... i can remember read it in de re atari

Think I remember seeing this listing for SIO usage. thanks, I'll have to dig out my original hard copy of De Re and read up.

[tebe]

Tezz, it's C (cc65 is a small C for 8-bit computers)

 

www.cc65.org

http://atariarea.histeria.pl/artykuly.php?...z_artykul&id=45

[Tezz]

tebe Tezz, it's C (cc65 is a small C for 8-bit computers)  

 

www.cc65.org  http://atariarea.histeria.pl/artykuly.php?akcja=pokaz_artykul&id=45

 

Cool, missed that one, didn't know that there was a C compiler for the A8. Gonna check that one right out!

[tebe]

compiler for PC, Linux, OS/2

 

ftp://ftp.musoftware.de/pub/uz/cc65/

 

atari library "cc65-atari-2.10.0-1.zip"

cc65 compiler for win32 "cc65-win32-2.10.0a-1.zip"