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:
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.
See also: MetaDOS Function list