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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 distinguishes whether the address is for memory or IO. This is a Read control signal active low. They have higher priority than the INTR interrupt. In the previous articles we saw about the architecture of microprocessor.

It has to be acknowledged. It cannot be enabled or disabled using a program.

Pin Diagram and Pin description of Microprocessor

These signals are used for giving serial input and output data. Signals which aids in supplying power and generating frequency are associated with this type. Among the interrupts of microprocessor, TRAP is the only non-maskable interrupt.

S0 and S1 are status signals which provides different status and functions depending on their status. The lower order address bus is added to memory or any external latch. Consider we have an address to be processed.

Pin Diagram and Pin description of 8085 Microprocessor

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 frequency is internally divided by two; therefore to operate a system at 3 MHz, the crystal should have frequency of 6 Mhz. This is an active high output signal used to indicate that the microprocessor is reset. Signals associated with the lower order address bus and time multiplexed higher order address bus comes under this type of signals.


This is an active high, serial output port pin, used to transfer serial 1 bit data under software control. This pin provides serial input data. A crystal or RC, LC network is connected to these two pins. These pins are used for least significant bits of address bus in the first machine clock cycle and used as data bus for second and third clock cycle.

READY is used by the microprocessor to check whether a peripheral is ready to accept or transfer data. These 8 signal lines are unidirectional and used for most significant bits called higher order address bus of a bit address.

Microprocessor – 8085 Pin Configuration

Power supply and Frequency signals: The CPU is held in reset condition until this pin is high. This pin is used for hold acknowledgement. Pin are vectored interrupt that transfer the program control to specific memory location. This signal can be used as the system clock for other devices.

Pin Diagram and Pin description of

Signals associated with data bus comes under this type. It has the lowest priority among the interrupts. A peripheral may be a LCD display or analog to digital converter or any other. That is, an operation is performed when the signal goes low. 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. They are used as lower order address bus as well as data bus. When HOLD pin is activated by an external signal the expplanation relinquishes control of buses and allows the external pheripheral to use them. They insert an internal restart function automatically. While the diatram goes low, the address is assigned for the memory. Fiagram two peripheral devices. These are the terminals which are connected to external oscillator to produce the necessary and suitable clock operation.


Classification of Signals The various signals in a microprocessor can be classified as Power supply and Frequency signals: Pin Diagram of Microprocessor and its description is as follows: When it is high.

Such signals come under this category. This indicates if any other device is requesting the use of micrpprocessor and data bus.

All the above mentioned interrupts are maskable interrupts. The serial data on this pin is loaded into the seventh bit of the accumulator when RIM instruction is executed. AD 0 -AD 7.

The serial data on this pin delivers its output to the seventh bit of the accumulator when SIM instruction is executed. 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, they can be enabled or disabled using microprocessof.

This pin resets the program counter to 0 and resets interrupt enable and HLDA flip-flops. It has the highest priority among the interrupts.

This signal is used to control READ operation of the microprocessor. This is an active low signal.

This is used to acknowledge interrupt.