Table of Contents
8085 Architecture
Intel is firstly created the Intel 8085, in 1977. It has potential to operate eight-bit at a time. In 8085 microprocessor is created by N-MOS technology. The main reason to build the 8085 microprocessor is to create a simple and cost effective microcomputer system. This can perform arithmetic and logical operations, provide temp memory for string the addresses.
Different Units of 8085 Architecture
Below is a list of a microprocessor’s various units:
- Accumulator
- Arithmetic and logic unit
- General purpose register
- Program counter
- Stack pointer
- Temporary Register
- Flags
- Instruction register and Decoder.
- Timing and Control unit
- Interrupt control
- Address buffer and Address-Data buffer
- Address bus and Data bus
Accumulator
The accumulator helps to store two amounts. The accumulator holds the data that the logic and arithmetic units will process. Additionally, it saves the outcome of the computation that the Arithmetic and Logic unit performed. Another name for the accumulator is an 8-bit register. The internal data bus and ALU (arithmetic and logic unit) are connected to the accumulator. Data from the Internal Data bus can be sent to and received from the accumulator.
Arithmetic and Logic Unit (ALU)
Arithmetic operations like +, -, *, and /, as well as logical operations like AND, OR, NOT, and so on are always necessary. Thus, there is need to establish a distinct unit that can carry out these kinds of tasks. The ALU is responsible for carrying out these operations (ALU). These procedures are carried out on 8-bit data via ALU. However, these procedures cannot be carried out without some input (or data) that the intended operation is to be carried out. Thus, how do these inputs go to the ALU? An accumulator is used for this. The temporary register and accumulator provide the input for the ALU.After processing the necessary operations, the result is stored back in accumulator.
General Purpose Registers
8085 is made up of six unique register types known as General Purpose Registers in addition to the accumulator.
The general-purpose The 8085 processors’ registers are B, C, D, E, H, and L. Each Register has an 8-bit data capacity. In addition to the use above, these registers can store 16-bit data when used in pairs. They can store 16-bit data by cooperating in pairs like B-C, D-E, and H-L. The H-L pair serves as a pointer to memory. An address of a specific memory location is stored in a memory pointer. They have 16-bit storage capacity.
Program Counter
The program counter is a special-purpose register. Consider that processor is executing an instruction. As soon as the After the ALU has completed processing an instruction, the processor searches for the following command to be performed. Therefore, in order to save time, it is necessary to hold the address of the next instruction that needs to be executed.
Stack Pointer
A stack pointer is a type of register or small type register that can store the memory address of previous data and add it to be in the stack. The stack pointer in the 8085 microprocessor has 16-bit register value which can store the address of the top of the stack memory.
Temporary Register
Register Temporary This register serves as a temporary memory during arithmetic and logical operations, as its name would imply. This temporary register is totally inaccessible to programmers and is only accessible by the microprocessor, in contrast to other registers. Eight bits make up the Temporary Register.
Flag Register
All that flags are is a collection of single flip-flops. The flags are primarily connected to operations in logic and arithmetic. Depending on the data circumstances in the accumulator or different registers, the flags will display a logical (0 or 1), or a set or reset. In reality, a flag is just a latch that can store some data. It notifies the processor that an event has occurred.
Intel processors have a set of 5 flags:
- Carry flag
- Parity flag
- Auxiliary carry flag
- Zero flag
- Sign flag
For Example
1100 0000 1000 0000 The most significant bit generates a carry when the two numbers above are added. The number in the extreme right is least significant bit, while the number in the extreme left is the most significant bit. Thus, the carry causes the generation of a ninth bit. How can I accommodate 9th bit in an 8-bit register? For this purpose, the Carry flag is used. Every time a carry is generated, the carry flag is set; it is reset when no carry is found.
Instruction Register and Decoder
Like all other microprocessor registers, the instruction register is an 8-bit register. Think of a directive. The instructions could be anything from copying data to moving data or adding two data, among other things. An instruction of this type is sent to the instruction register when it is retrieved from memory. Thus, the purpose of the instruction registers is to hold the instructions that are retrieved from memory.
Timing and Control Unit
The timing and control unit transmits the control signals required for both internal and external control of data and other units. It is composed of an oscillator and a controller sequencer. The oscillator produces two-phase clock signals that help synchronise the 8085 microprocessor’s registers. Now whenever the interrupt signal is enabled or requested the microprocessor shifts the control from primary software to handle the incoming request.
Interrupt signals present in 8085 are:
- INTR
- RST 7.5
- RST 6.5
- RST 5.5
- TRAP
Address Buffer and Address-Data buffer
The address buffer and address-data buffer are filled with the contents of the program counter and stack pointer. These buffers then drive the address-data bus and external address bus. Data from the internal data bus can be sent and received via the address data buffer.
Address Bus and Data Bus
Thus, eight bits of data can be sent to or received by the microprocessor.. But, the 8085 processor requires a 16-bit address bus as the memory addresses are 16-bit wide. The address/data bus is time multiplexed.
Frequently Asked Questions (FAQs)
Explain what is 8085 ?
A microprocessor with eight bits of memory that stores and processes data using a series of instructions called an instruction cycle.
Define different instruction sets?
CISC ISAs provide a more extensive collection of instructions, whereas RISC ISAs contain a more condensed set of efficient, basic instructions.
How data transfer between registers?
The data transfer operation between registers is MOV, MVI, LXI
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