GeneveOS Device Operation

Accessing devices (floppy disk, hard disk, serial connector, printer) is possible in GeneveOS via XOP calls.

User-task XOPs

User-task XOPs are available for use in application programs. Here is a typical example:

PABADD EQU  >F180   
FILE   DATA 8
...
       LI   R0,PABADD
       XOP  @FILE,0
       MOVB @PABADD+2,R0
       JNE  SF7
       ...

Similar as with the TI-99/4A device service routine concept (DSR), a Peripheral Access Block (PAB) must be set up prior to invoking the XOP.

Available memory pages

Opcode: 0

	Input	Output
R0	Opcode (0000)	Error code (always 0)
R1		Number of free pages
R2		Number of fast free pages
R3		Total number of pages in system

This function is used to query the free space in the system. No changes are applied. The total number of pages are the maximum number of allocatable pages.