8051 ADD Instruction

Addition

Instruction	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
Variants	ADD A,Rn ADD A,direct address ADD A,@Ri ADD A, #immediate data

Instruction	ADD A,Rn
Bytes	1
Cycles	1
Encoding	0 0 1 0 1 n n n
Operation	A = A + Rn
Flags Affected	C AC F0 RS1 RS0 OV P
Example	ADD A, R0
Bytes: Number of bytes required to encode the instruction. Cycles: Number of instruction cycles required to execute the instruction. Note that there are 12 oscillator cycles to one instruction cycle on a standard 8051. Encoding: Lists the byte encoding for the instruction. Operation: Lists, step-by-step, the operations performed by the instruction. Flags Affected: are highlighted in Bold

Instruction	ADD A,direct address
Bytes	2
Cycles	1
Encoding	0 0 1 0 0 1 0 1 A7...A0
Operation	A = A + (direct)
Flags Affected	C AC F0 RS1 RS0 OV P
Example	ADD A, 20h
Bytes: Number of bytes required to encode the instruction. Cycles: Number of instruction cycles required to execute the instruction. Note that there are 12 oscillator cycles to one instruction cycle on a standard 8051. Encoding: Lists the byte encoding for the instruction. Operation: Lists, step-by-step, the operations performed by the instruction. Flags Affected: are highlighted in Bold

Instruction	ADD A,@Ri
Bytes	1
Cycles	1
Encoding	0 0 1 0 0 1 1 i
Operation	A = A + (Ri)
Flags Affected	C AC F0 RS1 RS0 OV P
Example	ADD A, @R1
Bytes: Number of bytes required to encode the instruction. Cycles: Number of instruction cycles required to execute the instruction. Note that there are 12 oscillator cycles to one instruction cycle on a standard 8051. Encoding: Lists the byte encoding for the instruction. Operation: Lists, step-by-step, the operations performed by the instruction. Flags Affected: are highlighted in Bold

Instruction	ADD A, #immediate data
Bytes	2
Cycles	1
Encoding	0 0 1 0 0 1 0 0 D7...D0
Operation	A = A + immediate data
Flags Affected	C AC F0 RS1 RS0 OV P
Example	ADD A, #03h
Bytes: Number of bytes required to encode the instruction. Cycles: Number of instruction cycles required to execute the instruction. Note that there are 12 oscillator cycles to one instruction cycle on a standard 8051. Encoding: Lists the byte encoding for the instruction. Operation: Lists, step-by-step, the operations performed by the instruction. Flags Affected: are highlighted in Bold

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Related topics:
8051 Arithmetic Operation Instructions   |   8051 ADDC Instruction   |   8051 SUBB Instruction   |   8051 INC Instruction   |   8051 DEC Instruction   |   8051 MUL Instruction   |   8051 DIV Instruction   |   8051 DA Instruction

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List of topics: 8051

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