h6. [[OS SWI Calls]] h6(. » [[OS_ChangeEnvironment]] h6((. » UpCall Handler h2. UpCall Handler |_<^{width:3em}. Entry | | |<^. R0 |<^. "Reason code":OS_UpCall#reason | |<^. R12|<^. Workspace pointer | |\2<^. All other registers dependent on reason code | |\2<^. SVC mode, IRQ+FIQ state undefined | h4. Use Called by the kernel to warn an applications of particular situations. If the UpCall handler is called and R0 = [[OS_UpCall 256|UpCall_NewApplication (256)]], all handlers should be restored to their previous values and you should then return to the caller preserving all registers, letting the new application start. h4. See also * [[OS_UpCall]]