Interfacing Stepper Motor to 8086 using 8255 Diagram

Explain with a neat diagram the interfacing of stepper motor to 8086 using 8255 in detail

The integration of a stepper motor with an 8086 microprocessor is made seamless through the use of the 8255 Programmable Peripheral Interface (PPI). The detailed walkthrough, complete Interfacing of Stepper Motor to 8086 using 8255 with a connection diagram and programming insights, to empower enthusiasts and engineers in the realm of microprocessor-controlled stepper motor applications.

Components Overview:

  1. 8086 Microprocessor:
    • The central processing unit that governs the overall system.
  2. 8255 PPI:
    • A programmable chip that extends additional Input/Output (I/O) ports to the 8086, facilitating communication with external devices.
  3. Stepper Motor:
    • A specialized motor that rotates in precise increments, responding to electrical pulses.
  4. Driver Circuit:
    • An electronic circuit responsible for amplifying signals from the 8255, which are then used to drive the coils of the stepper motor.

Connection Diagram:

  • Data Lines:
  • Connect the data lines (D0-D7) of the 8255 to the corresponding data lines of the 8086 for data transfer.
  • Address/Control Lines:
  • Link the address/control lines (A0-A2, CS, RD, WR) of the 8255 to the corresponding lines on the 8086 used for I/O operations.
  • Ports:
  • Port A/B:
    • Connect the four bits of Port A or B (PA0-PA3 or PB0-PB3) to the driver circuit, controlling the stepper motor coils.
  • Port C:
    • Use Port C (PC0-PC7) for additional control signals such as direction, step pulse, and enable.


  • Employ Assembly Language Programming (ALP) to configure 8255 ports and govern the stepper motor.
  • Set the appropriate mode for Ports A/B and Port C using the control registers of the 8255.
  • Write the desired bit sequence to Ports A/B to energize the stepper motor coils for rotation.
  • Use Port C for controlling direction, step pulse timing, and enabling/disabling the motor.


  1. The 8086 issues instructions and data to the 8255 through address/control and data lines.
  2. The 8255 decodes instructions, configuring its ports based on the mode settings.
  3. The 8086 writes the motor control sequence to Port A/B.
  4. The driver circuit amplifies Port A/B signals, driving the stepper motor coils in the specified sequence.
  5. The coil sequence energizes in a specific order, causing the motor shaft to rotate as desired.

Additional Notes:

  • Specific connections and programming steps may vary based on the stepper motor and driver circuit used.
  • Consider factors such as pulse timing, current requirements, and direction control for optimal motor performance.
  • Ensure proper heat dissipation for the driver circuit, especially when dealing with high currents.

By grasping this interfacing approach, individuals can leverage their 8086-based systems to control stepper motors for diverse applications like robotic arm movement, 3D printing, and CNC machines. This guide serves as a foundation for enthusiasts and engineers diving into the exciting world of microprocessor-driven stepper motor applications.