PM0214 datasheet(95/245 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.

3.5.12

SHSUB16 and SHSUB8

Signed halving subtract 16 and Signed halving subtract 8

Syntax

op{cond}{Rd,} Rn, Rm

where:

•

op is any of:

SHSUB16: Signed halving subtract 16

SHSUB8: Signed halving subtract 8

•

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

•

‘Rd’ is the destination register

•

‘Rn’ is the register holding the operand

•

‘Rm’ is the second operand register

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 SHSUB16 instruction:

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

the first operand.

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

Writes the halved halfword results in the destination register.

The SHSUBB8 instruction:

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

operand,

Shuffles the result by one bit to the right, halving the data,

Writes the corresponding signed byte results in the destination register.

Restrictions

Do not use SP and do not use PC.

Condition flags

These instructions do not change the flags.

Examples

SHSUB16 R1, R0

; Subtracts halfwords in R0 from corresponding halfword

; of R1 and writes to corresponding halfword of R1

SHSUB8

R4, R0, R5

; Subtracts bytes of R0 from corresponding byte in R5,

; and writes to corresponding byte in R4.

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