Draw the Pin configuration of 8086 up and explain the functioning of all the Pins.

The 8086 microprocessor, a pivotal component in the evolution of computing, boasts a sophisticated architecture encapsulated in its 40-pin configuration. Arranged in two rows of 20 pins each, these pins play crucial roles in powering, addressing, and controlling the 8086. From grounding and power supply pins to intricate data and address lines, clock synchronization, interrupts, and control signals, each pin serves a distinct function, orchestrating the seamless execution of instructions. This article is explanation of “Pin diagram of 8086 and Functions of its 40 Pins”.

The Pin Diagram of 8086 is:

8086 Pin Configuration and Functions

Power Supply Pins

  • Ground Pins (1, 20): Connect to the ground (GND) of the power supply, providing a reference for electrical potential.
  • +5V Power Supply (40): Connects to the +5V power supply (VCC), ensuring proper voltage for the chip’s operation.

Address Lines

  • Address Lines (2-17): 16 lines (A0-A15) used to identify memory or I/O device locations for read or write operations.

Data Lines

  • Data Lines (34-39): 16 lines (D0-D15) for data transfer between the 8086 processor and memory or I/O devices.

Clock and Reset

  • Clock Input (19): Receives clock signal (CLK) for synchronization of 8086 operations.
  • Reset Input (21): Initializes and starts execution from the boot program when a reset signal is received.


  • Interrupt Request (18): Signal (INTR) for external interrupts.
  • Non-Maskable Interrupt (17): Signal (NMI) for non-maskable interrupts.

Additional Control Inputs

  • Test Input (23): Puts 8086 into test mode for debugging (TEST’).
  • Ready Input (22): Allows the 8086 to stall execution if memory or I/O devices are not ready (READY).
  • Memory/I/O Select Pin (33): Informs 8086 whether it is accessing memory or an I/O device (MN/MX’).

Output Pins

  • Output Pins (24-25): Output data to external devices (QSO and QS1).


  • Address Latch Enable (26): Enables latching of the address onto the address bus (ALE).

Control Pins

  • Control Pins (27-30): DEN’, DT/R’, S1′, and S2′ control various aspects of the 8086 operation.

Request/Grant Lines

  • Request/Grant Lines (31-32): RQ/GT0′ and RQ/GT1′ implement a bus request/grant scheme for memory and I/O devices.

Chip Selection

  • Active-High Chip Select Pin (35): A19/S6 pin used to select the 8086 chip.

Address/Data Lines

  • Address/Data Lines (36-38): A16/S3, A17/S4, and A18/S5 serve dual purposes for both address and data transfers.
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