The interrupt return pointer register (IRP) contains the return pointer that directs the CPU to the proper location to continue program execution after processing a maskable interrupt (INT15-INT4, SWI, or UNDEF). A branch using the address in IRP (BIRP) in your interrupt service routine returns to the program flow when interrupt servicing is complete. The IRP is shown in Figure 8-37 and described in Table 8-321.
Figure 8-37 Interrupt Return Pointer Register (IRP) | LEGEND: R = Readable by the MVC instruction; W = Writeable by the MVC instruction; -x = value is indeterminate after reset |
Table 8-321 Interrupt Return Pointer Register (IRP) Field Descriptions| Bit | Field | Value | Description |
|---|
| 31 | Reserved | 0 | Reserved. The reserved bit location is always read as 0. A value written to this field has no effect. |
| 30-0 | Return Address | 0-7FFF FFFFh | Contains the return address. It is written by the CPU while taking an interrupt. It is read by the CPU to execute the BIRP instruction. |