Escape Handler (changes)
Showing changes from revision #4 to #5:
Added | Removed | Changed
OS SWI Calls
» OS_ChangeEnvironment
» Escape Handler
Escape Handler
| Entry | |
|---|---|
| R11 | Bit 6: |
| 0 => Escape condition is being cleared/acknowledged | |
| 1 => Escape condition is being set | |
| R12 | “workspace” – don’t use the value 1 |
| R13 | SVC/IRQ stack |
| SVC or IRQ mode, IRQs+FIQs undefined |
| Exit | |
|---|---|
| R12 | 1 to set callback |
| R0-R11 | Preserved |
Use
This handler allows programs to control how Escape events are handled.
Notes
This is called whenever an escape condition is detected and the escape event is disabled (except for calls to OS_Byte 125 which always call the handler).
OS_Byte 124 and OS_Byte 126 will also result in the handler being called with R11 bit 6 clear to clear/acknowledge an escape condition.
If the handler returns with R12=1, a non-transient callback will be queued.
See also
Social
Follow us on
and
and
ROOL Store
Buy RISC OS Open merchandise here, including SD cards for Raspberry Pi and more.