8085A

Intel 8085 8-bit Microprocessor Intel 8085 is an 8-bit, NMOS microprocessor. It is a 40 pin C package fabricated on a single LSI chip. The Intel 8085A uses a single +5V D.C supply for its operation. Its clock speed is about 3 MHz. The clock cycle is of 320 ns. The time for the back cycle of the Intel 8085 A-2 is 200 ns. It has 80 basic instructions and 246 opcodes. Figure 1 shows the block diagram of Intel 8085A. It consists of three main sections, an arithmetic and logic unit a timing and control unit and several registers. These important sections are described as under. ALU The arithmetic and logic unit, ALU performs the following arithmetic and logic operations. 1. Addition 2. Subtraction 3. Logical AND 4. Logical OR 5. Logical EXCLUSIVE OR 6. Complement (logical NOT) 7. Increment (add 1) 8. Decrement (subtract 1) 9. Left shift (add input to itself) 10. Clear (result is zero) Timing and Control Unit The timing and control unit is a section of the CPU. It generates timing and control signals which are necessary for the execution of instructions. It controls provides status, control and timing signals which are required for the operation of memory and I/O 1 devices. It controls the entire operation of the microprocessor and peripherals consented to it. Thus it is seen that control unit of the CPU acts as a brain of the computer. Registers Figure 1 show the various registers of Intel 8085A. Registers are small memories within the CPU. They are used by the microprocessor for...