stw or st (Store) instruction
Purpose
Stores a word of data from a general-purpose register into a specified location in memory.
Syntax
| Bits | Value |
|---|---|
| 0 - 5 | 36 |
| 6 - 10 | RS |
| 11 - 15 | RA |
| 16 - 31 | D |
Description
The stw and st instructions store a word from general-purpose register (GPR) RS into a word of storage addressed by the effective address (EA).
If GPR RA is not 0, the EA is the sum of the contents of GPR RA and D, a 16-bit signed two's complement integer sign-extended to 32 bits. If GPR RA is 0, then the EA is D.
The stw and st instructions have one syntax form and do not affect the Fixed-Point Exception Register or Condition Register Field 0.
Parameters
| Item | Description |
|---|---|
| RS | Specifies source general-purpose register of stored data. |
| D | Specifies a16-bit signed two's complement integer sign-extended to 32 bits for EA calculation. |
| RA | Specifies source general-purpose register for EA calculation. |
Examples
The following code stores the contents of GPR 6 into a location in memory:
.csect data[rw]
buffer: .long 0,0
# Assume GPR 6 contains 0x9000 3000.
# Assume GPR 5 contains the address of buffer.
.csect text[pr]
stw 6,4(5)
# 0x9000 3000 is now stored at the address buffer+4.