Instruction type ORI d8 in 8085 Microprocessor

Microprocessor8085

In 8085 Instruction set, ORI is a mnemonic that stands for “OR Immediate with Accumulator” and “d8” stands for any 8-bit data. This instruction is used to OR 8-bit immediate data with the Accumulator. The result of ORing will be stored in the Accumulator itself. As it is a logical instruction, the S, P, and Z flags are affected based on the result. Cy and AC are reset to 0. It occupies 2-Bytes in memory.

Mnemonics, Operand Opcode(in HEX) Bytes
ORI Data F6 2

Let us consider ORI CDH as an example instruction of this category. As it is a 2-Byte instruction so it will occupy 2 consecutive memory locations. We are considering initial content of Accumulator is ABH. The result of execution of this instruction has been shown in the following tracing table.

Before After

(A)

ABH EFH

(F)

Any values Cy=0,AC=0,S=1,P=0,Z=0

The internal calculation has been done as shown below −

(A) ABH ---> 1010 1011
(d8) CDH ---> 1100 1101
              ---------
      ORICDH ---> 1110 1111 (EFH)

Address Hex Codes Mnemonic Comment
2002 F6 ORI CDH A = A or CDH
2003 CD Operand CDH

The timing diagram against this instruction ORI CDH execution is as follows.

ORI CDH

Summary − So this instruction ORI CDH requires 2-Bytes, 2-Machine Cycles (Opcode Fetch, Memory Read) and 7 T-States for execution as shown in the timing diagram.

raja
Published on 04-Dec-2018 12:09:20
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