Atmel 8051 User Manual

The 8051 Instruction Set
1-25 Atmel 8051 Microcontrollers Hardware Manual
4316B–8051–02/04
1.14.2 ADD A,<src-byte>
Function: Add
Description: ADD adds the byte variable indicated to the Accumulator, leaving the result in the Accumulator. The carry and
auxiliary-carry flags are set, respectively, if there is a carry-out from bit 7 or bit 3, and cleared otherwise. When
adding unsigned integers, the carry flag indicates an overflow occurred.
OV is set if there is a carry-out of bit 6 but not out of bit 7, or a carry-out of bit 7 but not bit 6; otherwise, OV is
cleared. When adding signed integers, OV indicates a negative number produced as the sum of two positive
operands, or a positive sum from two negative operands.
Four source operand addressing modes are allowed: register, direct, register-indirect, or immediate.
Example: The Accumulator holds 0C3H (1100001lB), and register 0 holds 0AAH (10101010B). The following instruction,
ADD A,R0
leaves 6DH (01101101B) in the Accumulator with the AC flag cleared and both the carry flag and OV set to 1.
ADD A,R
n
Bytes: 1
Cycles: 1
Encoding: 00101r r r
Operation: ADD
(A) ← (A) + (R
n
)
ADD A,direct
Bytes: 2
Cycles: 1
Encoding: 00100101 direct address
Operation: ADD
(A) ← (A) + (direct)
ADD A,@R
i
Bytes: 1
Cycles: 1
Encoding: 0010011 i
Operation: ADD
(A) ← (A) + ((R
i
))
ADD A,#data
Bytes: 2
Cycles: 1
Encoding: 00100100 immediate data
Operation: ADD
(A) ← (A) + #data

Atmel 8051 Specifications

General

Brand	Atmel
Model	8051
Category	Microcontrollers
Language	English