ADC

ADC

Instruction	ADC[S]
Function	Add with Carry
Category	Data processing
ARM family	All
Notes	-

ADC[S] : Add with Carry

ADC will add two values and the Carry flag.

Operand 1 is a register, operand 2 can be a register, shifted register, or an immediate value (which may be shifted).

If the S bit is set (ADCS), the N and Z flags are set according to the result, and the C and V flags are set as follows: C if the result generated a carry (unsigned overflow); V if the result generated a signed overflow.

ADC is useful for multiword addition, for example adding two 64 bit values. Use ADD for basic addition.

Syntax

  ADC<suffix>  <dest>, <op 1>, <op 2>

Function

  dest = op_1 + op_2 + Carry

Example

If R0-R1 is a 64 bit value, and R2-R3 is another 64 bit value, the code below will add them, placing the result in R4-R5.

  ADDS R4, R0, R2
  ADC  R5, R1, R3

Technical

The instruction bit pattern is as follows:

31 - 28	27	26	25	24 - 21	20	19 - 16	15 - 12	11 - 0
condition	0	0	I	0 1 0 1	S	op_1	dest	op_2/shift

Note: If the I bit is zero, and bits 4 and 7 are both one (with bits 5,6 zero), the instruction is UMLAL, not ADC.