Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 155

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

Sign extend and Zero extend.

Syntax

op{cond} {Rd,} Rm {, ROR #n}

op{cond} {Rd}, Rm {, ROR #n}

where:

op

is one of:

SXTB Sign extends an 8-bit value to a 32-bit value.

SXTH Sign extends a 16-bit value to a 32-bit value.

SXTB16 Sign extends two 8-bit values to two 16-bit values.

UXTB Zero extends an 8-bit value to a 32-bit value.

UXTH Zero extends a 16-bit value to a 32-bit value.

UXTB16 Zero extends two 8-bit values to two 16-bit values.

cond

Rd

is the destination register.

Rm

is the register holding the value to extend.

ROR #n

is one of:

ROR #8 Value from Rm is rotated right 8 bits.

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.



SXTB16 extracts bits[7:0] and sign extends to 16 bits,
and extracts bits [23:16] and sign extends to 16 bits.



UXTB16 extracts bits[7:0] and zero extends to 16 bits,
and extracts bits [23:16] and zero extends to 16 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

; 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