10.172 USAD8

Unsigned Sum of Absolute Differences.


USAD8{cond} {Rd}, Rn, Rm
is an optional condition code.
is the destination register.
is the register holding the first operand.
is the register holding the second operand.


The USAD8 instruction finds the four differences between the unsigned values in corresponding bytes of Rn and Rm. It adds the absolute values of the four differences, 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.


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.


    USAD8       r2, r4, r6
Related reference
10.8 Condition code suffixes
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