The 8085 Microprocessor

Generation of Control Signals  In any system, there are different modes of operations. Likewise, in some situation we are interested to read data in microprocessor, in other we are interested to write data on some location from microprocessor. Whenever, we are dealing with different peripherals using 8085 microprocessor there are two modes of operations. One is to read data from any of the memory device or input device. Second is to write data on some location, this location can be any of the output device location or any of the memory location. To deal with these modes 8085 microprocessor architecture gives three different control signals. Namely IO/ M , RD  and  WR . The  IO/ M  is an output pin of the 8085 microprocessor which serves dual purpose, the high going pulse on this pin indicates the I/O type of operation. We can state that, at this time 8085 is working with the input or output devices. The low going pulse on this pin indicates the memory operation. The second one is

Instruction Set of 8085 An instruction is a binary pattern designed inside a microprocessor to perform a specific function. The entire group of instructions, called the instruction set , determines what functions the microprocessor can perform. These instructions can be classified into the following five functional categories: data transfer (copy)   operations, arithmetic operations, logical operations, branching operations, and machine-control operations. Data Transfer (Copy) Operations This group of instructions copy data from a location called a source to another location called a destination, without modifying the contents of the source. In technical manuals, the term data transfer is used for this copying function. However, the term transfer is misleading; it creates the impression that the contents of the source are destroyed when, in fact, the contents are retained without any modification. The various types of data transfer (copy) are listed below together with example