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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Pin Diagram and Pin description of Microprocessor

Diagra clock cycle is nothing but the time taken between two adjacent pulses of the oscillator. That is, an operation is performed when the signal goes low.

They have higher priority than the INTR interrupt. S0 and S1 are status signals which provides different status and functions depending on their status. 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.

They are time multiplexed.

The frequency is internally divided by two; therefore to operate a system at 3 MHz, the crystal should have frequency of 6 Mhz. Whenever the microprocessor receives interrupt signal.

This is a Write control signal active low. AD 0 -AD 7. This signal goes high during the first clock cycle and enables the lower order 808 bits. They are used as lower order address bus as well siagram data bus. Pin Diagram of Microprocessor and its description is as follows: Classification of Signals The various signals in a microprocessor can be classified as Power supply and Frequency signals: This is an active high, serial output port pin, used to transfer serial 1 bit data under microprocfssor control.


In this article let us discuss in detail about the various signals involved in transferring data and executing instructions in microprocessor. These pins are multiplexed to be used as address bus as well as data bus.

This signal is used to reset other devices in system. Pin are vectored interrupt that transfer the program control to specific explanagion location.

Consider we have an address to be processed. Pin-wise description of is as follows. They insert an internal restart function automatically. The lower order address bus is added to memory or any external latch.

Pin Diagram and Pin description of 8085 Microprocessor

This is used to acknowledge interrupt. The CPU is held in reset condition until this pin is high. Signals associated with data bus comes under this type.

It cannot be enabled or disabled using a program. That is, they can be enabled or disabled using programs. Its frequency is always same as the frequency at explanayion the microprocessor operates. These signals are used for giving serial input and output data. Consider two peripheral devices. It has to be acknowledged.

A peripheral may be a LCD display or analog to digital converter or any other. This pin is used for hold acknowledgement. When the reset pin is activated by an external key all explanatoon internal operations are suspended and the program counter is cleared and the program execution begins at zero memory address. The serial data on this pin delivers its output to the seventh bit of the accumulator when SIM instruction is executed. In the previous article we saw how ALE helps in demultiplexing the lower order address and data bus.


While the pin goes low, the address is assigned for the memory. The pins A8-A15 denote the address bus. When it is high. This is an active low signal. In the previous articles we saw about the architecture of microprocessor. INTR can be enabled or disabled by using software.

These pins are mciroprocessor for least significant bits of address bus in the first machine clock cycle and used as data bus for second and third clock cycle.

This indicates if any other device is requesting the use of address and data bus. So the first clock cycle means the first transition of pulse from 0volts to 5 volts and then back to 0 volts. This is a Read control signal active low. 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

This signal can be used as the system clock for other devices. This is a non-maskable interrupt and has highest priority. Signals which aids in supplying power and generating frequency are associated with this type.

It indicates whether the HOLD signal is received or not. It is ground reference. This signal is primarily used to synchronize slower peripherals with the microprocessor. Explanarion like Vcc and ground are classified under this type.