8051 INC Instruction

Increment

Instruction	INC byte
Function	Increment
Description	INC increments the indicated variable by 1. An original value of 0FFH overflows to 00H. No flags are affected. Three addressing modes are allowed: register, direct, or register-indirect. Note: When this instruction is used to modify an output port, the value used as the original port data will be read from the output data latch, not the input pins.
Example	Register 0 contai ns 7EH (011111110B) . I nternal RAM l ocati ons 7EH and 7FH contain 0FFH and 40H, respectively. The following instruction sequence, INC @R0 INC R0 INC @R0 leaves register 0 set to 7FH and internal RAM locations 7EH and 7FH holding 00H and 41H, respectively.
Variants	INC A INC Rn INC direct address INC @Ri

Instruction	INC A
Bytes	1
Cycles	1
Encoding	0 0 0 0 0 1 0 0
Operation	A = A + 1
Flags Affected	C AC F0 RS1 RS0 OV P
Example	INC A
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	INC Rn
Bytes	1
Cycles	1
Encoding	0 0 0 0 1 n n n
Operation	Rn = Rn + 1
Flags Affected	C AC F0 RS1 RS0 OV P
Example	INC R4
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	INC direct address
Bytes	2
Cycles	1
Encoding	0 0 0 0 0 1 0 1 A7...A0
Operation	(direct) = (direct) + 1
Flags Affected	C AC F0 RS1 RS0 OV P
Example	INC 34h
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	INC @Ri
Bytes	1
Cycles	1
Encoding	0 0 0 0 0 1 1 i
Operation	(Ri) = (Ri) + 1
Flags Affected	C AC F0 RS1 RS0 OV P
Example	INC @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	INC DPTR
Function	Increment Data Pointer
Bytes	1
Cycles	2
Encoding	1 0 1 0 0 0 1 1
Operation	DPTR = DPTR + 1
Description	INC DPTR increments the 16-bit data pointer by 1. A 16-bit increment (modulo 216) is performed, and an overflow of the low-order byte of the data pointer (DPL) from 0FFH to 00H increments the high-order byte (DPH). No flags are affected. This is the only 16-bit register which can be incremented.
Flags Affected	C AC F0 RS1 RS0 OV P
Example	Registers DPH and DPL contain 12H and 0FEH, respectively. The following instruction sequence, INC DPTR INC DPTR INC DPTR changes DPH and DPL to 13H and 01H.
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 ADD Instruction   |   8051 ADDC Instruction   |   8051 SUBB 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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