The Intel (“eighty-eighty-five”) is an 8-bit microprocessor produced by Intel and introduced in It is a software-binary compatible with the more-famous. Microprocessor: It is a programmable electronics chip (Integrated Circuit ( IC)). A single IC has computing and decision making capabilities similar to. In addition to the microprocessor, a personal computer has a keyboard for The AS/ uses the PowerPC microprocessor with its reduced instruction set.

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A downside compared to similar contemporary designs such as the Z80 is the fact that the buses require demultiplexing; however, address latches in the Intel, and memory chips allow a direct interface, so an along with these chips is almost a complete system. It is a bit register used to mixroprocessor the memory address location of the next instruction to be executed.

A bus is a group of wires lines that carry similar information. An instruction is a command to the microprocessor to perform a given task on a specified data. The contents of the accumulator are copied into the memory location specified by the contents of the operand. For example, multiplication is implemented microrocessor a multiplication algorithm.

When an instruction of data transfer group kicroprocessor executed, data is transferred from the source to the destination without altering the contents of the source. In the previous article we saw how ALE helps in demultiplexing the lower order address and data bus.

8085 Data-transfer Instructions

Operations that have to be implemented by program code subroutine libraries include comparisons of signed integers as well as multiplication and division. These signals are used for giving serial input and output data.


The lower order address bus is added to memory or any external latch. The sign flag is set if the result has a negative sign i. The instruction loads the contents of the H and L registers into the stack pointer register. A peripheral microprocessir be a LCD display or analog to digital converter or any other.

Microprocessor Architecture

S0 and S1 are status signals which provides different status and functions depending on their status. The stack pointer register is decremented again and the contents of the low-order register C, E, L, flags are copied to that location.

READY is used by the microprocessor to check whether a peripheral is ready to accept or transfer data. There are also eight one-byte call instructions RST for subroutines located at the fixed addresses 00h, 08h, 10h, INTR can be enabled or disabled by using software.

All interrupts are enabled by the EI instruction and disabled by the DI instruction. The architecture of consists of three main sections, ALU Arithmetic and Logical Unittiming and control unit and Registers shown in the following figure.

The DMA controller takes control of the buses and transfers data directly between source and destination, thus bypassing the microprocessor.

Microprocessor – 8085 Architecture

Three control signals are available on chip: The content stored in the stack pointer and program counter is loaded into the address buffer and address-data buffer to communicate with the CPU. Used to accept data from outside devices to store in the accumulator or send the data stored in the accumulator to the outside device.


Signals which aids in supplying power and generating frequency are associated with this type. It can be used to store additional data during a program. It can also accept a second processor, allowing a limited form of multi-processor operation where both processors run mixroprocessor and independently.

It also has a bit program counter and a bit stack pointer to memory replacing the ‘s internal stack.

Whenever INTR goes high the microprocessor completes the current instruction which is being executed and then acknowledges microprocedsor INTR signal and processes it. It generates timing and 80055 signals, which are necessary for the execution of instructions. Its frequency is always same as the frequency at which the microprocessor operates.

Write assembly program for multiplying two 8 bit numbers. Operands are internal registers and are coded into the instruction. Week 8 Aug 27 30 upvotes. Some instructions use HL as a limited bit accumulator. Load the accumulator indirect. Exceptions include timing-critical code and code that is sensitive to the aforementioned difference in the AC flag setting or differences in undocumented CPU behavior.

Signals associated with the lower order address bus and time multiplexed higher order address bus comes under this type of signals. The size of the address bus determines the size of memory, which can be used.

The number of bits that can be stored in a register or memory element is called a memory word.

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