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

173

SAM4S Series [DATASHEET]

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

These instructions do not affect the flags.
Examples

SXTH

R4, R6, ROR #16

; Rotates R6 right by 16 bits, obtains bottom halfword of

; of result, sign extends to 32 bits and writes to R4

UXTB

R3, R10

; Extracts lowest byte of value in R10, zero extends, and

; writes to R3.

Signed and Unsigned Extend and Add
Syntax

op{cond} {Rd,} Rn, Rm {, ROR #n}

op{cond} {Rd,} Rn, Rm {, ROR #n}

where:
opis one of:
SXTAB Sign extends an 8-bit value to a 32-bit value and add.
SXTAH Sign extends a 16-bit value to a 32-bit value and add.
SXTAB16 Sign extends two 8-bit values to two 16-bit values and add.
UXTAB Zero extends an 8-bit value to a 32-bit value and add.
UXTAH Zero extends a 16-bit value to a 32-bit value and add.
UXTAB16 Zero extends two 8-bit values to two 16-bit values and add.
condis an optional condition code, see 

.

Rdis the destination register.
Rnis the first operand register.
Rmis the register holding the value to rotate and 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:

̶

SXTAB extracts bits[7:0] from Rm and sign extends to 32 bits.

̶

UXTAB extracts bits[7:0] from Rm and zero extends to 32 bits.

̶

SXTAH extracts bits[15:0] from Rm and sign extends to 32 bits.

̶

UXTAH extracts bits[15:0] from Rm and zero extends to 32 bits.

̶

SXTAB16 extracts bits[7:0] from Rm and sign extends to 16 bits,

and extracts bits [23:16] from Rm and sign extends to 16 bits.

̶

UXTAB16 extracts bits[7:0] from Rm and zero extends to 16 bits,

and extracts bits [23:16] from Rm and zero extends to 16 bits.