Basic Operations of 8085 Microprocessor
The 8085 microprocessor performs followings five basic operations .
1. Opcode Fetch : Reading and decoding operation code of n instruction.
2. Memory Read: Reading data from memory.
3. Memory Write : Writing data into memory.
4. I. O Read: Accepting data from input port.
5. I/ O Write : Sending data to output port.
These operations will be discussed in detail with their timing diagrams in chapter6.
Here only memory read operation is explained to show how different busses are used together to perform such operations.
Suppose data byte stored at location 2010H is to be read in memory read operation followings steps are followed to perform this operations:
1. The 16 bit memory address is placed on the 16bit address bus by the microprocessor.
2. The address is decoded by the memory decoder and the desired memory location is selected.
3. For reading the data from this location a RD signal is generated by the control unit of the microprocessor which enables the memory chip.
4. The data byte from the memory location is placed on the data bus.
5. Through data bus data byte is brought into the microprocessor register.