MDOS XOP Definitions

From Ninerpedia
Jump to navigation Jump to search

MDOS makes frequent use of XOPs and offers them for user programs. An XOP (extended operation) is a special command of the TMS processor family which causes a context switch, transferring control to a location that is specified in a table.

Compared to common architecture concepts, the XOP is TI's way of implementing a system call. All system calls are XOP 0 with specific arguments:

ARGUM  DATA <number>
       ...
       XOP  @ARGUM,0
       ...
XOP argument Category
5 Keyboard
6 Video display
7 Memory Management
8 Device Operation
9 Utility functions
10 Mathematical functions