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13.153 SXTB

Sign extend Byte, to extend an 8-bit value to a 32-bit value.

Syntax

SXTB{cond} {Rd}, Rm {,rotation}

where:

cond

is an optional condition code.

Rd

is the destination register.

Rm

is the register holding the value to extend.

rotation

is one of:

ROR #8

Value from Rm isrotated right 8 bits.

ROR #16

Value from Rm isrotated right 16 bits.

ROR #24

Value from Rm isrotated right 24 bits.

If rotation is omitted, norotation is performed.

Operation

This instruction does the following:

  1. Rotates the value from Rm rightby 0, 8, 16 or 24 bits.

  2. Extracts bits[7:0] from the value obtained.

  3. Sign extends to 32 bits.

Register restrictions

You cannot use PC for any operand.

You can use SP in A32 instructions but this is deprecated. You cannot use SP in T32 instructions.

Condition flags

This instruction does not change the flags.

16-bit instructions

The following form of this instruction is available in T32 code, and is a 16-bit instruction:

SXTB Rd, Rm

Rd and Rm mustboth be Lo registers.

Availability

The 32-bit instruction is available in A32 and T32.

The 16-bit instruction is available in T32.

Related reference