sthbrx (Store Half Byte-Reverse Indexed) instruction
Purpose
Stores a halfword of data from a general-purpose register into a specified location in memory with the two bytes reversed.
Syntax
| Bits | Value |
|---|---|
| 0 - 5 | 31 |
| 6 - 10 | RS |
| 11 - 15 | RA |
| 16 -20 | RB |
| 21 - 30 | 918 |
| 31 | / |
Description
The sthbrx instruction stores bits 16-31 of general-purpose register (GPR) RS into the halfword of storage addressed by the effective address (EA).
Consider the following when using the sthbrx instruction:
- Bits 24-31 of GPR RS are stored into bits 00-07 of the halfword in storage addressed by EA.
- Bits 16-23 of GPR RS are stored into bits 08-15 of the word in storage addressed by EA.
If GPR RA is not 0, the EA is the sum of the contents of GPR RA and GPR RB. If GPR RA is 0, then the EA is the contents of GPR RB.
The sthbrx instruction has one syntax form and does not affect the Fixed-Point Exception Register or Condition Register Field 0.
Parameters
| Item | Description |
|---|---|
| RS | Specifies source general-purpose register of stored data. |
| RA | Specifies source general-purpose register for EA calculation. |
| RB | Specifies source general-purpose register for EA calculation. |
Examples
The following code stores the halfword contents of GPR 6 with the bytes reversed into a location in memory:
.csect data[rw]
buffer: .long 0
# Assume GPR 6 contains 0x9000 3456.
# Assume GPR 4 contains the address of buffer.
.csect text[pr]
sthbrx 6,0,4
# buffer now contains 0x5634.