Sxt And Uxt - ST STM32F4 Series Programming Manual

PM0214
3.8.2

SXT and UXT

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' is an optional condition code (see
•
'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.
ROR #16 Value from Rm is rotated right 16 bits.
ROR #24 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.
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.
Conditional execution on page
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The STM32 Cortex-M4 instruction set
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