11.175 USAD8

Unsigned Sum of Absolute Differences.

Syntax

USAD8{cond} {Rd}, Rn, Rm

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.

Operation

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.

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.

Example

    USAD8       r2, r4, r6
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