Datasheet

130
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
Rd is the destination register.
Rn is the register holding the first operand.
Rm is the register holding the second operand.
Operation
Use these instructions to add 16- and 8-bit data and then to halve the result before writing the result to the destination
register:
The UHADD16 instruction:
1. Adds each halfword from the first operand to the corresponding halfword of the second operand.
2. Shuffles the halfword result by one bit to the right, halving the data.
3. Writes the unsigned results to the corresponding halfword in the destination register.
The UHADD8 instruction:
1. Adds each byte of the first operand to the corresponding byte of the second operand.
2. Shuffles the byte result by one bit to the right, halving the data.
3. Writes the unsigned results in the corresponding byte in the destination register.
Restrictions
Do not use SP and do not use PC
.
Condition Flags
These instructions do not change the flags.
Examples
UHADD16 R7, R3 ; Adds halfwords in R7 to corresponding halfword of R3
; and writes halved result to corresponding halfword
; in R7
UHADD8 R4, R0, R5 ; Adds bytes of R0 to corresponding byte in R5 and
; writes halved result to corresponding byte in R4.
12.6.5.19 UHASX and UHSAX
Unsigned Halving Add and Subtract with Exchange and Unsigned Halving Subtract and Add with Exchange.
Syntax
op{cond} {Rd}, Rn, Rm
where:
op is one of:
UHASX Add and Subtract with Exchange and Halving.
UHSAX Subtract and Add with Exchange and Halving.
cond is an optional condition code, see “Conditional Execution” .
Rd is the destination register.
Rn, Rm are registers holding the first and second operands.
Operation
The UHASX instruction:
1. Adds the top halfword of the first operand with the bottom halfword of the second operand.
2. Shifts the result by one bit to the right causing a divide by two, or halving.
3. Writes the halfword result of the addition to the top halfword of the destination register.
4. Subtracts the top halfword of the second operand from the bottom highword of the first operand.
5. Shifts the result by one bit to the right causing a divide by two, or halving.