Usada8 - ST STM32F4 Series Programming Manual

The STM32 Cortex-M4 instruction set
3.5.23

USADA8

Unsigned Sum of Absolute Differences and Accumulate
Syntax
USADA8{cond}{Rd,} Rn, Rm, Ra
Where:
• 'cond' is an optional condition code (see
•
'Rd' is the destination register.
•
'Rn' is the first operand register.
•
'Rm' is the second operand register.
•
'Ra' is the register that contains the accumulation value.
Operation
The USADA8 instruction:
1. Subtracts each byte of the second operand register from the corresponding byte of the
first operand register.
2. Adds the unsigned absolute differences together.
3. Adds the accumulation value to the sum of the absolute differences.
4. Writes the result to the destination register.
Restrictions
Do not use SP and do not use PC.
Condition flags
These instructions do not change the flags.
Examples
USADA8 R1, R0, R6 ; Subtracts bytes in R0 from corresponding halfword of R1
USADA8 R4, R0, R5, R2 ; Subtracts bytes of R5 from corresponding byte in R0
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; adds differences, adds value of R6, writes to R1
; adds differences, adds value of R2 writes to R4.
DocID022708 Rev 6
Conditional execution on page
PM0214
64).