SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The shadow control status register (SCSR) contains a copy of the control status register (CSR) (of background code) in the interrupt context (except for an NMI). The SCSR is shown in Figure 8-48 and described in Table 8-330.
On acceptance of an interrupt (except for an NMI), the current state of the control status register (CSR) is copied to SCSR. On execution of a BIRP instruction, SCSR is copied back to CSR. SCSR facilitates fast interrupt response. A write to SCSR has no effect on machine operation.
| 31 | 16 |
| Reserved |
| R-0 |
| 15 | 14 | 13 | 12 | 11 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| Reserved | DBZ | DBZE | INUM | V | SAT | C | GT | LT | EQ | Rsvd | GIE | ||||
| R-0 | R/W-0 | R/W-0 | R/W-0 | R/W-0 | R/W-0 | R/W-0 | R/W-0 | R/W-0 | R/W-0 | R-0 | R/W-0 | ||||
| LEGEND: R = Readable by the MVC instruction; W = Writeable by the MVC instruction; -n = value after reset |
| Bit | Field | Value | Description |
|---|---|---|---|
| 31-14 | Reserved | 0 | Reserved. The reserved bit location is always read as 0. A value written to this field has no effect. |
| 13 | DBZ | 0-1 | Shadow copy of CSR:DBZ bit. |
| 12 | DBZE | 0-1 | Shadow copy of CSR:DBZE bit. |
| 11-8 | INUM | 0-Fh | Shadow copy of CSR:INUM field. |
| 7 | V | 0-1 | Shadow copy of CSR:V bit. |
| 6 | SAT | 0-1 | Shadow copy of CSR:SAT bit. |
| 5 | C | 0-1 | Shadow copy of CSR:C bit. |
| 4 | GT | 0-1 | Shadow copy of CSR:GT bit. |
| 3 | LT | 0-1 | Shadow copy of CSR:LT bit. |
| 2 | EQ | 0-1 | Shadow copy of CSR:EQ bit. |
| 1 | Reserved | 0 | Reserved. The reserved bit location is always read as 0. A value written to this field has no effect. |
| 0 | GIE | 0-1 | Shadow copy of CSR:GIE bit. |