Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

178

Sign extend and Zero extend.
Syntax

SXTextend{cond} {Rd,} Rm {, ROR #n}

UXTextend{cond} {Rd}, Rm {, ROR #n}

where:
extendis one of:
B Extends an 8-bit value to a 32-bit value.
H Extends a 16-bit value to a 32-bit value.
condis an optional condition code, see 

.

Rdis the destination register.
Rmis the register holding the value to extend.
ROR #nis one of:
ROR #8 Value from Rm is rotated right 8 bits.
ROR #16 

Value from Rm is rotated right 16 bits.

Value from Rm is rotated right 24 bits.

If ROR #n is omitted, no rotation is performed.
Operation
These instructions do the following:

1. Rotate the value from Rm right by 0, 8, 16 or 24 bits.

2. Extract bits from the resulting value:

̶

SXTB extracts bits[7:0] and sign extends to 32 bits.

̶

UXTB extracts bits[7:0] and zero extends to 32 bits.

̶

SXTH extracts bits[15:0] and sign extends to 32 bits.

̶

UXTH extracts bits[15:0] and zero extends to 32 bits.

Restrictions
Do not use SP and do not use PC.
Condition Flags
These instructions do not affect the flags.
Examples

SXTH

R4, R6, ROR #16

; Rotate R6 right by 16 bits, then obtain the lower

; halfword of the result and then sign extend to

; 32 bits and write the result to R4.

UXTB

R3, R10

; Extract lowest byte of the value in R10 and zero

; extend it, and write the result to R3.