sthx
Store Halfword Indexed - 7C 00 00 1D
sthx

Instruction Syntax

Mnemonic Format Flags
sthx rS,rA,rB None

Instruction Encoding

0
1
1
1
1
1
S
S
S
S
S
A
A
A
A
A
B
B
B
B
B
0
0
0
0
0
0
0
0
0
0
0

Field Bits Description
Primary Opcode 0-5 011111 (0x1F)
rS 6-10 Source register
rA 11-15 Base register
rB 16-20 Index register
Reserved 21-29 000000000
Reserved 30-31 00

Operation

EA ← (rA) + (rB)
(EA) ← (rS)[16:31]

The effective address is calculated by adding the base register to the index register. The least significant halfword (bits 16-31) of the source register is stored at the effective address.

Note: The sthx instruction stores a 16-bit halfword to memory using indexed addressing. The address must be aligned to a 2-byte boundary.

Affected Registers

Memory

Examples

Basic Store Halfword Indexed

# Store halfword using indexed addressing
sthx r1, r3, r4     # Store r1 at address r3 + r4

Array of Halfwords with Dynamic Index

# Store halfword in array using dynamic index
li r3, array         # Load array base address
li r4, 4             # Index = 4 (2 * 2 bytes)
sthx r1, r3, r4      # Store halfword at array[2]

Dynamic Addressing

# Store halfword using dynamic index calculation
li r3, base_addr     # Load base address
add r4, r5, r6       # Calculate index dynamically
sthx r1, r3, r4      # Store halfword at base_addr + index

Related Instructions

sth, sthu, sthux, lhx

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