PM0214 datasheet(130/245 Pages) STMICROELECTRONICS

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The STM32 Cortex-M4 instruction set

PM0214

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DocID022708 Rev 4

3.7.6

UQASX and UQSAX

Saturating Add and Subtract with Exchange and Saturating Subtract and Add with

Exchange, unsigned.

Syntax

op{cond} {Rd}, Rm, Rn

where:

•

op’ is one of:

UQASX Add and Subtract with Exchange and Saturate.

UQSAX Subtract and Add with Exchange and Saturate.

•

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

•

‘Rd’ is the destination register.

•

‘Rn, Rm’ are registers holding the first and second operands.

Operation

The UQASX instruction:

Adds the bottom halfword of the source operand with top halfword of second operand.

Subtracts the bottom halfword of the second operand from the top highword of the first

operand.

Saturates the results of the sum and writes a 16-bit unsigned integer in the range

≤x ≤216 – 1, where x equals 16, to the top halfword of the destination register.

Saturates the result of the subtraction and writes a 16-bit unsigned integer in the range

≤x ≤216 – 1, where x equals 16, to the bottom halfword of the destination register.

The UQSAX instruction:

Subtracts the bottom halfword of second operand from top highword of first operand.

Adds the bottom halfword of the first operand with the top halfword of the second

operand.

Saturates the result of the subtraction and writes a 16-bit unsigned integer in the range

≤x ≤216 – 1, where x equals 16, to the top halfword of the destination register.

Saturates the results of the addition and writes a 16-bit unsigned integer in the range 0

≤x ≤216 – 1, where x equals 16, to the bottom halfword of the destination register.

Restrictions

Do not use SP and do not use PC.

Condition flags

These instructions do not affect the condition code flags.

Examples

UQASX

R7, R4, R2 ; Adds top halfword of R4 with bottom halfword of R2,

; saturates to 16 bits, writes to top halfword of R7

; Subtracts top halfword of R2 from bottom halfword of

; R4, saturates to 16 bits, writes to bottom halfword of R7

UQSAX

R0, R3, R5 ; Subtracts bottom halfword of R5 from top halfword of

; R3, saturates to 16 bits, writes to top halfword of R0

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