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ATSAM4S-XPLD
160
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
12.6.9.3 SXT and UXT
Sign extend and Zero extend.
Syntax
SXTextend{cond} {Rd,} Rm {, ROR #n}
UXTextend{cond} {Rd}, Rm {, ROR #n}
where:
extend
is one of:
B Extends an 8-bit value to a 32-bit value.
H Extends a 16-bit value to a 32-bit value.
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.
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.
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
; Rotate R6 right by 16 bits, then obtain the lower
; halfword of the result and then sign extend to
; 32 bits and write the result to R4.
UXTB
R3, R10
; Extract lowest byte of the value in R10 and zero
; extend it, and write the result to R3.