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Features of 8085 Microprocessor
In the field of computing and microprocessor technology, the 8085 Microprocessor is one of the most popular 8-bit microprocessors. It is known for paving the foundation for evolution of modern computing. The 8085 microprocessor was created by Intel Corporation in 1977 and widely used in early computing systems employed in educational applications. Learning about 8085-microprocessor can serve as a great stating point for beginners who wants to understand the world of microprocessors.
In this chapter, we will learn about some of the key Features of 8085 Microprocessor, from simple 8-bit architecture to memory addressing capability and direct memory access.
Features of 8085-Microprocessor
An in-depth overview of various features of the 8085 microprocessor is given below −
8-Bit Microprocessor
The 8085-microprocessor is an 8-bit microprocessor, which means it has a word length of 8 bits and thus can process 8-bits of digital data in one cycle. Because of this capability, it is widely used in applications that involve basic arithmetic and logical operations.
Uses N-MOS Technology
The 8085-microprocessor is manufactured by using NMOS (N-Channel Metal Oxide Semiconductor) technology. This provides an enhanced performance and reliability in operations.
16-Bit Address Bus
The 8085-microprocessor consists of a 16-bit address bus. Hence, it allows to transfer a maximum of 16-bit address and access 216 = 65,536 = up to 64 kB memory locations. This feature of the 8085-microprocessor makes it suitable to used in small to medium-scale applications.
8-Bit Data Bus
The 8085-microprocessor comprises an 8-bit data bus, therefore it can handle 8-bits of digital data simultaneously.
Multiplexed Address and Data Bus
In the 8085-microprocessor, the first 8 lines of the address bus (A0-A7) and 8 lines of the data bus (D0-D7) are multiplexed as AD0-AD7. This feature helps reducing the microprocessor’s pin count and simplifies the structure. However, it introduces the requirement for external latches to separate the address and data signals.
Power Supply
The 8085-microprocessor requires a power supply of +5 volts to operate efficiently.
Clock Frequency
The 8085-microprocessor uses a clock frequency of 3 MHz to 6 MHz, and it depends on the model of the processor. For example, 8085-2 has a clock frequency of 5 MHz, while P8085AH-1 has a clock frequency of 6 MHz. This range of clock frequency provides a reliable and smooth execution of instructions.
Dual-In-Line Package
The 8085-microprocessor is supplied in a 40-pin Dual-In-Line Package (DIP). This package provides an easy interfacing with other components in a circuit.
Register
The 8085-microprocessor comprises several different types of registers, as given below −
- It has six 8-bit general-purpose registers namely, B, C, D, E, H, and L. These registers are arranged in three pairs of 16-bit each, which are BC, DE, and HL.
- It also consists of a 16-bit stack pointer (SP) which points to the top of the stack in the memory.
- It consists of a 16-bit program counter (PC) to keep the track of the address of the next instruction that has to be executed.
On-Chip Clock Generator
The 8085-microprocessor also consists of an on-chip clock generator. This internal clock generator eliminates the need for an external clock circuit and it can operate by using a tuned circuit like RC, LC, or crystal oscillator.
Instruction Set and Addressing Modes
The 8085-microprocessor has 74 instructions with the support of following addressing modes −
- Immediate
- Register
- Direct
- Indirect
- Implied
Arithmetic Logic Unit (ALU)
The arithmetic logic unit of the 8085-microrpcoessor can perform the following functions −
- Addition of 8-bit binary numbers with or without carry
- Addition of 16-bit binary numbers
- Addition of 2-digit BCD (Binary Coded Decimal) numbers
- Subtraction of 8-bit binary numbers with or without borrow
- Logical operations such as OR, AND, NOT, XOR, and shift operations.
Hardware Interrupts
The 8085-microprocessor provides the following five hardware interrupts −
- TRAP
- RST 7.5
- RST 6.5
- RST 5.5
- INTR
Serial Communication
The 8085-microprocessor has serial I/O control which allows for efficient serial communication of data.
Control Signals
The 8085-microprocessor can produce control signals namely, IO/M, RD, WR to control the bus cycles without need for any external bus controller.
Direct Memory Access (DMA)
DMA is another key feature of the 8085-microprocessor. It allows the processor to transfer data between memory and I/O devices at a high-speed.
Three-Chip Microcomputer
The 8085-microprocessor can be combined with I/O ICs like 8155 and 8355 to implement a small-sized three-chip microcomputer.
Conclusion
In this chapter, we explained all the key features of 8085 microprocessor in a comprehensive manner. From the above discussion, we can conclude that the 8085-microprocessor has several features, making it an ideal choice in a variety of applications.