Datasheet

105
11011B–ATARM–21-Feb-12
SAM3N
10.13.1 ADD, ADC, SUB, SBC, and RSB
Add, Add with carry, Subtract, Subtract with carry, and Reverse Subtract.
10.13.1.1 Syntax
op{S}{cond} {Rd,} Rn, Operand2
op{cond} {Rd,} Rn, #imm12 ; ADD and SUB only
where:
op is one of:
ADD Add.
ADC Add with Carry.
SUB Subtract.
SBC Subtract with Carry.
RSB Reverse Subtract.
S is an optional suffix. If S is specified, the condition code flags are updated on the
result of the operation, see “Conditional execution” on page 84.
cond is an optional condition code, see “Conditional execution” on page 84.
Rd is the destination register. If Rd is omitted, the destination register is Rn.
Rn is the register holding the first operand.
Operand2 is a flexible second operand.
See “Flexible second operand” on page 80 for details of the options.
imm12 is any value in the range 0-4095.
10.13.1.2 Operation
The ADD instruction adds the value of Operand2 or imm12 to the value in Rn.
The ADC instruction adds the values in Rn and Operand2, together with the carry flag.
The SUB instruction subtracts the value of Operand2 or imm12 from the value in Rn.
The SBC instruction subtracts the value of Operand2 from the value in Rn. If the carry flag is
clear, the result is reduced by one.
The RSB instruction subtracts the value in Rn from the value of Operand2. This is useful
because of the wide range of options for Operand2.
Use ADC and SBC to synthesize multiword arithmetic, see “Multiword arithmetic examples” on
page 107.
See also “ADR” on page 88.
ADDW is equivalent to the ADD syntax that uses the imm12 operand. SUBW is equivalent to the
SUB syntax that uses the imm12 operand.
10.13.1.3 Restrictions
In these instructions:
• Operand2 must not be SP and must not be PC