1. 1 Q.1) Draw & Explain the Pin-Diagram of Microprocessor in Detail? Ans: The Microprocessor is an 8-Bit general-purpose. is a 40 pin IC, The signals from the pins can be grouped as follows Power supply and clock signals,Address bus,Data bus Pin Diagram and Pin description of It is used to know the type of current operation of the microprocessor. Microprocessor – All concepts, programming, interfacing and applications explained.

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These are the terminals which are connected to external oscillator to produce the necessary and suitable clock operation. Among the interrupts of microprocessor, TRAP is the only non-maskable interrupt. The lower order address bus is added to memory pij any external latch.

Signals associated with expanation lower order address bus and time multiplexed higher order address bus comes under this type of signals. These signals are used for giving serial input and output data. INTR is an interrupt request signal. This pin provides the serial output data. All the above mentioned interrupts are maskable interrupts. This pin is used for hold acknowledgement.

It indicates whether the HOLD signal is received or not. Whenever the microprocessor receives interrupt signal. That is, they can be enabled or disabled using programs.

It is ground reference. This is an active high, serial input port pin, used to accept serial 1 bit data under software control.

AD 0 -AD 7. This is used to acknowledge interrupt. The pins A8-A15 denote the address bus.


The frequency is internally divided by two; therefore to operate a system at 3 MHz, the crystal should have frequency of 6 Mhz. A clock cycle is nothing but the time taken between microprodessor adjacent pulses of the oscillator.

Pin Diagram and Pin description of Microprocessor

It cannot be enabled or disabled using a program. This signal goes high during the first clock cycle and enables the lower order address bits. So the first clock cycle means the first transition of pulse from 0volts to 5 volts and then back to 0 volts. When HOLD pin is activated by an external signal the microprocessor relinquishes control of buses and micropgocessor the external pheripheral to use them.

Microprocessor Pin Diagram Explained

Consider two peripheral devices. When the reset pin is activated by an external key all the internal operations are suspended and the program counter is cleared and the program execution begins at zero memory address. Control and Status Signals: The serial data on this pin is loaded into the seventh bit of the accumulator when RIM instruction is executed.

This is an active high, serial mciroprocessor port pin, used to transfer serial 1 bit data under software control. Pin are vectored interrupt that transfer the program control to specific memory location. They are used as lower order address bus as well as data bus. Signals associated with data bus comes under this type.

This is a Read control signal active low.

The serial data on this pin delivers its output to the seventh bit of the accumulator when SIM instruction is executed. This signal is used to reset other devices in system.


A peripheral may be a LCD display or analog to digital converter or any other. In this article let us discuss in detail about the various signals involved in transferring data and executing instructions in microprocessor. In simple words clock cycle refers to the transition between o volts to 5 volts and back to diagraam volts.

They are time multiplexed. It has the lowest priority among the interrupts.

8085 Microprocessor Pin Diagram Explained

They insert an internal restart function automatically. After the LCD process is over, the control is transferred back to analog and digital converter.

Such signals come under this category. Signals which aids in supplying power and generating frequency are associated with this type.

They are used for the most significant bit of memory address. This pin provides serial input data. This is a Write control signal active low. In the previous article we saw how ALE helps in demultiplexing the lower order address and data bus. When it is high. A crystal or RC, LC network is connected to these two pins.

Whenever INTR goes high the microprocessor completes the current instruction which is being executed and then acknowledges the INTR signal and processes it. That is, an operation is performed when the signal goes low. This is a non-maskable interrupt and has highest priority.

These are nothing but the restart interrupts.