Sxtb, Sxth, Uxtb And Uxth - ST STM32F0 Series Programming Manual

PM0215
3.5.8

SXTB, SXTH, UXTB and UXTH

Sign extend and Zero extend.
Syntax
SXTB Rd, Rm
SXTH Rd, Rm
UXTB Rd, Rm
UXTH Rd, Rm
where:
●
'Rd' is the destination register
● 'Rn' ,'Rm' are the registers holding the first and second operands
Operation
These instructions extract bits from the resulting value:
1. SXTB extracts bits[7:0] and sign extends to 32 bits
2. UXTB extracts bits[7:0] and zero extends to 32 bits
3. SXTH extracts bits[15:0] and sign extends to 32 bits
4. UXTH extracts bits[15:0] and zero extends to 32 bits.
Restrictions
In these instructions, Rd and Rm must only specify R0-R7.
Condition flags
These instructions do not affect the flags.
Examples
SXTH R4, R6
UXTB R3, R1
; Obtain the lower halfword of the
; value in R6 and then sign extend to
; 32 bits and write the result to R4.
; Extract lowest byte of the value in R10 and zero
; extend it, and write the result to R3
Doc ID 022979 Rev 1
The STM32 Cortex-M0 instruction set
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