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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This pin provides serial input data. Pin are vectored interrupt that transfer the program control to specific memory location. This is a Read control signal active low.

This is an active high, serial output port pin, used to transfer serial 1 bit data under software control. The serial data on this pin is loaded into the seventh bit of the accumulator when RIM instruction is executed.

It indicates whether the HOLD signal is received or not. Expkanation two peripheral devices.

Pin Diagram and Pin description of 8085 Microprocessor

INTR can be enabled or disabled by using software. When the reset pin is activated by an external key piin the internal operations are suspended and the program counter is cleared and the program execution begins at microprocezsor memory address. Such signals come under this category. Among the interrupts of microprocessor, TRAP is the only non-maskable interrupt. After the LCD process is over, the control is transferred back to analog and digital converter.


This is a non-maskable interrupt and has highest priority. The frequency is internally divided by two; therefore to operate a system at 3 MHz, the crystal should have frequency of 6 Mhz.

INTR is an interrupt request signal. In the previous microprcoessor we saw about the architecture of microprocessor. While the pin goes low, the address is assigned for the memory. Control and Status Signals: It cannot be enabled or disabled using a program. All the above mentioned interrupts are maskable interrupts. This is an active low signal.

Microprocessor Pin Configuration

When HOLD pin is activated by an external signal the microprocessor relinquishes control of buses and allows the external pheripheral to use them. When it is high.

This pin resets the program counter to 0 and resets interrupt enable and HLDA flip-flops. They have higher priority than the INTR interrupt. This pin is used for hold acknowledgement. The CPU is held in reset condition until this pin is high. Suppose if analog to digital converter is using the address and data bus and if LCD requests the use of address and data bus by giving HOLD signal, then the microprocessor transfers the control to the LCD as soon as the current cycle is over.

The pins A8-A15 denote the address bus. They insert an internal restart function automatically. It has the lowest priority among the interrupts.


A peripheral may be explanwtion 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.

AD 0 -AD 7. They are used as lower order address bus as well as data bus. This is provided by CLK pin. These pins are multiplexed to be used as address bus as well as data bus.

Whenever the microprocessor receives interrupt signal. Pins like Vcc and ground are classified under this type.

Signals associated with data bus comes under this type. In simple words clock cycle refers to the transition between o volts to 5 volts and back to 0 volts.

Microprocessor – 8085 Pin Configuration

A clock cycle is nothing but the time taken between two adjacent pulses of the oscillator. So the first clock cycle means the first transition of pulse from 0volts to 5 volts and then back to 0 volts.

It has the highest priority among the interrupts. Pin Diagram of Microprocessor and its description is as follows: In the previous article we saw how ALE helps in demultiplexing the lower order address and data bus.