8085 Microprocessor Branch Instructions

8085 Microprocessor Branch Instructions – The branch instructions allow the microprocessor to change the sequence of a program, either unconditionally or under certain test conditions. Branch instructions are classified as:

1. Unconditional
2. Conditional

Unconditional Branch Instructions

JMP Address (16-bit)	Jump unconditionally to the specified address and start execution from that address.
Operation	PC ← Address
Length	3 bytes
Addressing mode	Immediate addressing mode
Flags	Flags are not affected.

CALL Address (16-bit)	Jump unconditionally to the specified address after storing the address of the next instruction of the main program.
Operation	[SP – 1] ← PCH [SP – 1] ← PCL SP ← SP – 2 PC ← address
Length	3 bytes
Addressing mode	Immediate addressing mode
Flags	Flags are not affected.

RET	Return from the subroutine unconditionally. The returning address is obtained from the stack and loaded into the program counter (PC).
Operation	PCL ← [SP] PCH ← [SP + 1] SP ← SP + 2
Length	1 bytes
Addressing mode	Indirect addressing mode
Flags	Flags are not affected.

Conditional Branch Instructions

J condition address (16-bit)	Jump to the specific address if the condition is true.
Operation	If the condition is true PC ← address Else PC ← PC + 3
Length	3 bytes
Addressing mode	Direct addressing mode
Flags	Flags are checked but not affected.

The 8085 microprocessor has five flags. Out of these five, only four flags are available to the programmer to check the condition. The auxiliary carry (AC) flag is used internally and not available to the programmer to check the condition. Possible conditions for jump instruction are shown in the table below.

Instruction	Condition	Comments
JC Address (16-bit)	CY = 1	Jump if carry
JNC Address (16-bit)	CY = 0	Jump if no carry
JZ Address (16-bit)	Z = 1	Jump if zero
JNZ Address (16-bit)	Z = 0	Jump if not zero
JP Address (16-bit)	S = 0	Jump if positive
JM Address (16-bit)	S = 1	Jump if minus
JPE Address (16-bit)	P = 1	Jump if even parity
JPO Address (16-bit)	P = 0	Jump if odd parity

C condition address (16-bit)	Call the subroutine at the specified address if the condition is true.
Operation	If the condition is true [SP – 1] ← PCH [SP – 1] ← PCL PC ← Address Else PC ← PC + 3
Length	3 bytes
Addressing mode	Immediate addressing mode
Flags	Flags are checked but not affected.

Possible conditions for all instructions are shown in the table below.

Instruction	Condition	Comments
CC Address (16-bit)	CY = 1	Call if carry
CNC Address (16-bit)	CY = 0	Call if no carry
CZ Address (16-bit)	Z = 1	Call if zero
CNZ Address (16-bit)	Z = 0	Call if not zero
CP Address (16-bit)	S = 0	Call if positive
CM Address (16-bit)	S = 1	Call if negative
CPE Address (16-bit)	P = 1	Call if even parity
CPO Address (16-bit)	P = 0	Call if odd parity