Datasheet

123
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
12.6.5.11 SHASX and SHSAX
Signed Halving Add and Subtract with Exchange and Signed Halving Subtract and Add with Exchange.
Syntax
op{cond} {Rd}, Rn, Rm
where:
op is any of:
SHASX Add and Subtract with Exchange and Halving.
SHSAX 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 SHASX instruction:
1. Adds the top halfword of the first operand with the bottom halfword of the second operand.
2. Writes the halfword result of the addition to the top halfword of the destination register, shifted by one bit to the
right causing a divide by two, or halving.
3. Subtracts the top halfword of the second operand from the bottom highword of the first operand.
4. Writes the halfword result of the division in the bottom halfword of the destination register, shifted by one bit to the
right causing a divide by two, or halving.
The SHSAX instruction:
1. Subtracts the bottom halfword of the second operand from the top highword of the first operand.
2. Writes the halfword result of the addition to the bottom halfword of the destination register, shifted by one bit to the
right causing a divide by two, or halving.
3. Adds the bottom halfword of the first operand with the top halfword of the second operand.
4. Writes the halfword result of the division in the top halfword of the destination register, shifted by one bit to the right
causing a divide by two, or halving.
Restrictions
Do not use SP and do not use PC
.
Condition Flags
These instructions do not affect the condition code flags.