4.1 About the XBIOS

These functions enable ordered access to the various special chips in the Atari. They are called via the 680X0-trap #14 and should be used only if no routines of a higher level (GEMDOS, BIOS) are available that can be used instead of them. The XBIOS may be subdivided into the following function groups:

CENTScreen XBIOS extension
Crazy-Dots XBIOS extension
CT60 XBIOS extension
Date, Time and Timer
Drive functions
DSP programming
Hatari DHS XBIOS extension
Interface programming
Interrupt functions
Keyboard functions
MATRIX XBIOS extension
OverScan XBIOS extension
PCI-BIOS
Printer functions
Screen functions
Sound routines
Special commands

The XBIOS is reentrant in MagiC. This means that these functions can be called from interrupts as well (as long as the relevant supervisor stack does not overflow...).

The XBIOS takes its parameters from the stack, in reverse order; this means that the last argument from the parameter list is stored as the first on the stack. Function results are returned in the processor register d0. Only registers d3-d7 and a3-a7 are saved, all others may be altered by the call.