13.188 USADA8

Unsigned Sum of Absolute Differences and Accumulate.


USADA8{cond} Rd, Rn, Rm, Ra



is an optional condition code.


is the destination register.


is the register holding the first operand.


is the register holding the second operand.


is the register holding the accumulate operand.


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 operand.

You can use SP in A32 instructions but this is deprecated. You cannot use SP in T32 instructions.

Condition flags

This instruction does not alter any flags.


The 32-bit instruction is available in A32 and T32.

For the Armv7‑M architecture, the 32-bit T32 instruction is only available in an Arm®v7E-M implementation.

There is no 16-bit version of this instruction in T32.

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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