std (Store Double Word) instruction
Purpose
Store a doubleword of data from a general purpose register into a specified memory location.
Syntax
| Bits | Value |
|---|---|
| 0 - 5 | 62 |
| 6 - 10 | RS |
| 11 - 15 | RA |
| 16 - 29 | DS |
| 30 - 31 | 0 |
Description
The std instruction stores a doubleword in storage from the source general-purpose register (GPR) RS into the specified location in memory referenced by the effective address (EA).
DS is a 14-bit, signed two's complement number, which is sign-extended to 64 bits, and then multiplied by 4 to provide a displacement Disp. If GPR RA is not 0, the EA is the sum of the contents of GPR RA and Disp. If GPR RA is 0, then the EA is Disp.
Parameters
| Item | Description |
|---|---|
| RS | Specifies the source general-purpose register containing data. |
| Disp | Specifies a 16-bit signed number that is a multiple of 4. The assembler divides this number by 4 when generating the instruction. |
| RA | Specifies source general-purpose register for EA calculation. |
Implementation
This instruction is defined only for 64-bit implementations. Using it on a 32-bit implementation will cause the system illegal instruction error handler to be invoked.