OS_Memory 21 (changes)
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OS SWI Calls
» OS_Memory
» OS_Memory 21
OS_ Memory 21
(SWI &68)
| Entry | |
|---|---|
| R0 | 21 (&15), and flags |
| R1 | Physical address to map in (low 32 bits) |
| R2 | Physical address to map in (high 32 bits) |
| R3 | Size to map in |
| Exit | |
|---|---|
| R0 | Preserved |
| R1 | Preserved |
| R2 | Preserved |
| R3 | Logical address assigned |
Use
The purpose of this call is to permanently map in a region of IO memory at run-time.
This call was introduced in RISC OS 5.27, to improve upon the existing OS_Memory 13 call (which can only deal with 32-bit physical addresses). For compatibility with older OS versions, it’s recommended to use OS_Memory 13 whenever 32-bit physical addresses are sufficient.
See also
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