Hi

Michael Karas,

I think what I want to do is a little diferent from your code.
I haven't only the loader.

Actually I have a small "bios" that has the loader too.
Not so frequently, I may change the bios.
I have different applications programs. I have one for each customer.

So I need to change the bios system sometimes to update and make it better.
But the different versions of bios needs to be compatible with the applications as much as possible.
SO THE BIOS is NOT ACTUALLY FIX, it needs to change sometimes.

I am using P89C51RD2 with 64Kbytes for code, 8 Kbytes for data, 2Kbytes EEPROM.
LARGE MODEL

SCHEME have thought these:
CODE SPACE
=> 2 parts : bios and application
using jump table to fix bios function address

XDATA SPACE
=> 3 parts : global variables, bios XDATA and application XDATA

1 ==> _AT_ for absolute variables shared by bios and applicattion (XDATA), using the same declarations

2 ==> for XDATA BIOS SPACE = reentrant functions or NOOVERLAY , so I will not mess up the variables

3 ==> for XDATA application SPACE = using OVERLAY to optimize the data space

DATA and IDATA => reserved for STACK

THEN, I compile and link BIOS separated from Application.

C51 bios.c
A51 jmps.a51
BL51 bios.obj, jmps.obj

C51 application.c
A51 equs.a51
BL51 application.obj, equs.obj

I thank you for your code, I am studing it !
Furthermore, what do you think about my scheme ?

Annibal