11.176 USADA8

Unsigned Sum of Absolute Differences and Accumulate.

Syntax

USADA8{cond} Rd, Rn, Rm, Ra

where:

cond

is an optional condition code.

Rd

is the destination register.

Rn

is the register holding the first operand.

Rm

is the register holding the second operand.

Ra

is the register holding the accumulate operand.

Operation

The USADA8 instruction adds the absolute values of the four differences to the value in Ra, and saves the result to Rd.

Register restrictions

You cannot use PC for any register.

You can use SP in ARM instructions but this is deprecated in ARMv6T2 and above. You cannot use SP in Thumb instructions.

Condition flags

This instruction does not alter any flags.

Architectures

This ARM instruction is available in ARMv6 and above.

This 32-bit Thumb instruction is available in ARMv6T2 and above. For the ARMv7-M architecture, it is only available in an ARMv7E-M implementation.

There is no 16-bit version of this instruction in Thumb.

Correct examples

    USADA8      r0, r3, r5, r2
    USADA8VS    r0, r4, r0, r1

Incorrect examples

    USADA8      r2, r4, r6      ; USADA8 requires four registers
    USADA16     r0, r4, r0, r1  ; no such instruction
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