PM0215 datasheet(57/91 Pages) STMICROELECTRONICS

57 / 91 page

PM0215

The STM32 Cortex-M0 instruction set

Doc ID 022979 Rev 1

57/91

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:

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

In these instructions, Rd and Rm must only specify R0-R7.

Condition flags

These instructions do not affect the flags.

Examples

SXTH R4, R6

; Obtain the lower halfword of the

; value in R6 and then sign extend to

; 32 bits and write the result to R4.

UXTB R3, R1

; Extract lowest byte of the value in R10 and zero

; extend it, and write the result to R3

PM0215 数据表(PDF) 57 Page - STMicroelectronics

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