"Laurens Holst" <[EMAIL PROTECTED]> escribi�/wrote/kakimashita/escreveu/�crit:
> I need info on the Expanded BIOS (also known as H.BEXT, EXTBIO or #FFCA)!!!
Don't worry brave man! Konami Man goes to rescue you! (-v-)v
Expanded BIOS hook was designed to expand BIOS (then why it has a so
strange name?? X-D) in order to manage new devices. So it is used for
example by RS-232 and DOS 2 mapper support routines. Nowadays, also TSR
programs (MemmMan, NestorAcentos...) use it, because it provides a fixed
memory location to CALL in page 3.
How it works? You put a device ID number in register D, a function
number in register E, and registers AF, BC, HL depending of the calling
routine (you can't use alternative registers, nor indexed ones). DE is
always preserved when returning; AF, BC, DE depends on the calling
routine; alternative and indexed are corrupted.
Hot to patch it for your own use? First, you must select your own device
ID number. Of course it must be a number not used by anyone before, for
avoid computer crash when other TSR sre installed. Here is a list if ID
numbers which I know:
#00 y #01, used by RS-232 BIOS.
#04, used by DOS 2 mapper support routines.
#22, used by me! (NestorAcentos, NestorCDPlayer and all TSRs which name
is Nestor*.*) 8-)
#34, used by MWMPLAY by Ramones.
#4D, used by MemMan.
#F0, used by MGSDRV.
It is recommended that once selected, you use always this number in your
programs, modifying register E for every program. For example I use
DE=#2200 for NestorAcentos, and DE=#2201 for NestorCDPlayer.
Now you must patch hook #FFCA, of course saving previous value. The
new jump routine must do this:
- Check D. If it does not match with your ID number, jump to the old
hook without any register modified.
- If it matches, check register E for required function, do anything and
return preserving DE.
This jump routine should be placed in page 3 if the program is a TSR.
How to reserve memory on page 3 is another question.
> Can't anybody help me???
I hope I helped you! 8-) If you want I can send some source code about
this (for example, source of NestorAcentos).
Hasta incluso!
*** NEXT BARCELONA MSX USERS MEETING: DECEMBER 4th ***
------------------------------------------------------------------------------------------------------
Konami Man - AKA Nestor Soriano (^ ^)v
Itsumo MSX user
[EMAIL PROTECTED]
http://konamiman.msx.tni.nl
User error. Please replace user and press any key.
------------------------------------------------------------------------------------------------------
****
MSX Mailinglist. To unsubscribe, send an email to [EMAIL PROTECTED] and put
in the body (not subject) "unsubscribe msx [EMAIL PROTECTED]" (without the
quotes :-) Problems? contact [EMAIL PROTECTED] (www.stack.nl/~wiebe/mailinglist/)
****
