Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Instruction type ORA R in 8085 Microprocessor
In 8085 Instruction set, ORA is a mnemonic, which stands for “OR Accumulator” and “R” stands for any of the following registers, or memory location M pointed by HL pair.
R = A, B, C, D, E, H, L, or M
This instruction is used to OR contents of R with the Accumulator. The result of OR operation will be stored back in the Accumulator. As R can have any of the eight values, there are eight opcodes for this type of instruction. It occupies only 1-Byte in memory.
| Mnemonics, Operand | Opcode(in HEX) | Bytes |
|---|---|---|
| ORA A | B7 | 1 |
| ORA B | B0 | 1 |
| ORA C | B1 | 1 |
| ORA D | B2 | 1 |
| ORA E | B3 | 1 |
| ORA H | B4 | 1 |
| ORA L | B5 | 1 |
| ORA M | B6 | 1 |
Let us consider the instruction ORA E as an example instruction of this category. As it is a 1-Byte instruction so it will occupy a single Byte in the memory. Let us consider that the initial contents of Accumulator and E register are ABH and CDH. The result of execution of this instruction has been shown in the following tracing table.
| Before | After | |
|---|---|---|
(E) |
CDH | CDH |
(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
(E) CDH ---> 1100 1101
---------
ORA E ---> 1110 1111 (EFH)
| Address | Hex Codes | Mnemonic | Comment |
|---|---|---|---|
| 2004 | B3 | ORA E | A = A OR E |
The timing diagram against this instruction ORA E execution is as follows −
Summary − So this instruction ORA E requires 1-Byte, 1-Machine Cycle (Opcode Fetch) and 4 T-States for execution as shown in the timing diagram.
5K+ Views
