PM0214 datasheet(103/245 Pages) STMICROELECTRONICS

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PM0214

The STM32 Cortex-M4 instruction set

244

; Adds top halfword of R5 to bottom halfword of R3 and

; writes halved result to bottom halfword of R0.

3.5.20

UHSUB16 and UHSUB8

Unsigned halving subtract 16 and Unsigned halving subtract 8

Syntax

op{cond}{Rd,} Rn, Rm

where:

•

op is any of:

UHSUB16: Performs two unsigned 16-bit integer additions, halves the results, and

writes the results to the destination register.

UHSUB8: Performs four unsigned 8-bit integer additions, halves the results, and writes

the results to the destination register.

•

‘cond’ is an optional condition code (see Conditional execution on page 64)

•

‘Rd’ is the destination register

•

‘Rn’ is the first register holding the operand

•

‘Rm’ is the second register holding the operand

Operation

Use these instructions to add 16-bit and 8-bit data and then to halve the result before writing

the result to the destination register:

The UHSUB16 instruction:

Subtracts each halfword of the second operand from the corresponding halfword of the

first operand.

Shuffles each halfword result to the right by one bit, halving the data.

Writes each unsigned halfword result to corresponding halfword in destination register.

The UHSUB8 instruction:

Subtracts each byte of second operand from the corresponding byte of the first

operand.

Shuffles each byte result by one bit to the right, halving the data.

Writes the unsigned byte results to the corresponding byte of the destination register.

Restrictions

Do not use SP and do not use PC.

Condition flags

These instructions do not change the flags.

Examples

UHSUB16 R1, R0

; Subtracts halfwords in R0 from corresponding R1 halfword

; and writes halved result to corresponding halfword in R1

UHSUB8

R4, R0, R5 ; Subtracts bytes of R5 from corresponding byte in R0 and

; writes halved result to corresponding byte in R4.

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