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Instruction type ORI d8 in 8085 Microprocessor
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.
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.
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