Hardware interrupts: TRAP, RST 7.5, RST 6.5,RST 5.5 and INTR.
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What is Microprocessor It is a program controlled semiconductor device ( IC), which fetches, decodes and executes instructions. What are the basic units of a microprocessor The basic units or blocks of a microprocessor are ALU, an array of registers and control unit. What is Software and Hardware The Software is a set of instructions or commands needed for performing a specific task by a programmable device or a computing machine. 8085 Microprocessor Programming Examples Software Can BeThe Hardware refers to the components or devices used to form computing machine in which the software can be run and tested. Without software the Hardware is an idle machine. What is assembly language The language in which the mnemonics (short -hand form of instructions) are used to write a program is called assembly language. The manufacturers of microprocessor give the mnemonics. What are machine language and assembly language programs The software developed using 1s and 0s are called machine lan guage, programs. The software developed using mnemonics are called assembly language programs. What is the drawback in machine language and assembly language, programs The machine language and assembly language programs are machine dependent. Define bit, byte and word. Also, the bit is the fundamental storage unit of computer memor y. The 8-bit (8-digit) binary number or code is called byte and 16-bit binary number or code is called word. Some microprocessor manufactures refer the basic data size operated by the processor as word). What is a bus Bus is a group of conducting lines that carries data, address and control signals. Why data bus is bi-directional The microprocessor has to fetch (read) the data from memory or input device for processing and after processing, it has to store (write) the data to memory or output device. Hence the data bus is bi-directional. Why address bus is unidirectional The address is an identification number used by the microprocessor to identify or access a memory location or I O device. Hence the address bus is unidirectional. What is the function of microprocessor in a system The microprocessor is the master in the system, which controls all the activity of the system. It iss ues address and control signals and fetches the instruction and data from memory. Then it executes the instruction to take appropriate action. How many machine cycles constitute one instruction cycle in 8085 Each instruction of the 8085 processor consists of one to five machine cycles. Define opcode and operand. Opcode (Operation code) is the part of an instr uction directive that identifies a specific operation. Operand is a part of an instruction directive that represents a value on which the instruction acts. What is opcode fetch cycle The opcode fetch cycle is a machine c ycle executed to fetch the opcode of an instruction stored in memory. Every instruction starts with opcode fetch machine cycle. What operation is performed during first T -state of every machine cycle in 8085 In 8085, during the first T -state of every machine cycle the low byte address is latched into an external latch using ALE signal. Why status signals are provided in microprocessor The status signals can be used by the s ystem designer to track the internal operations of the processor. Also, it can be used for memor y expansion (by providin g separate memory banks for program data and selecting the bank using status signals). How the 8085 proc essor differentiates a memory access (readwrite) and 10 access (readwrite) The memory access and 10 access is differentiated using 10 I M signal. The 8085 processor asserts 10 I M low for memory readwrite operation and 10 I M is asserted high for 10 readwrite operation. What is interrupt acknowledge cycle The interrupt acknowledge cycle is a ma chine c ycle executed by 8085 processor to get the address of the interrupt service routine in-order to service the interrupt device. These instructions are inserted at desired locations in a pr ogram. While running a pro gram, if software interrupt instruction is encountered then the processor executes an interrupt service routine. What is Hardware interrupt If an interrupt is initiated in a processor b y an appropriate signal at the interrupt pin, then the interrupt is called Hardware interrupt. What is the difference between Hardware and Software interrupt The Software interrupt is initiated by the main program, but the Hardware interrupt is initiated by an external device. In 8085, the Software in terrupt cannot be disabled or masked but the Hardware interrupt except TRAP can be disabled or masked. What is vectored and Non- Vectored interrupt When an interrupt is accepted, if the processo r control branches to a specific address defined by the manufacturer then the interrupt is called vectored interrupt. In Non-vectored interrupt there is no specific address for storing the interrupt ser vice routine. Hence the interrupted device should give the address of the interrupt service routine. List the Software and Hardware interrupts of 8085 Software interrupts: RST 0, RSTl, RST 2,RST 3, RST 4, RST 5,RST 6 and RST 7.
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