Write an assembly language program to interface stepper motor with 8085.

Aim

Write an assembly language program to interface stepper motor with 8085.

Apparatus:8085 microprocessor kit.

Stepper motor Interfacing/Control using 8085

Stepper MotorA stepper motor is a device that translates electrical pulses into mechanical movement in steps of fixed step angle.

1. The stepper motor rotates in steps in response to the applied signals.
2. It is mainly used for position control
3. It is used in disk drives, dot matrix printers, plotters and robotics and process control circuits

Operation The important parameter of a stepper motor is the step angle. It is the minimum angle through which the motor rotates in response to each excitation pulse. In a four phase motor if there are 200 steps in one complete rotation then then the step angle is 360/200 = 1.8O . So to rotate the stepper motor we have to apply the excitation pulse. For this the controller should send a hexa decimal code through one of its ports. The hex code mainly depends on the construction of the stepper motor. So, all the stepper motors do not have the same Hex code for their rotation.

The flow graph for the process of interfacing is shown as below:

Procedure:

Locate 26 pin connector J3 on DYNA-85LU kit. All the lines of the 8255 PIO are brought out on this connector.

The PIO cards are interfaced through 26 pin FRC flat cable.

1. Connect the PIO card to DYNA-85LU (J3) through 26 pin FRC flat cable as shown below:

2. The program for all the PIO cards are given in an EPROM (2732) labeled PIO-MON. Place EPROM in socket U3 of DYNA_85LU kit. Do the appropriate jumper setting for 2732 EPROM
3. The Program can be entered in two ways:

a. Copy the program from the specified RAM location as: DYNA-85> C 4700 49FF C000 Enter

b. Enter the program given as below:

4. Run the program from C000.

Program:The assembly program, when executed will display the message “Stepper mode (0 or 1)”. If 0 is given, the motor will run continuously and if 1 is given, the motor will run for a specified no. of steps, direction and speed.

0 Continuous Mode:In this mode, motor will run continuously at the maximum speed and in the clockwise direction. To stop it, Press ESC key.

1 Step Mode:The program will display message „stepper mode (0 or 1)‟. Enter 1 to switch to step mode. Then the program will display „rP (0 or 1)‟ asking for the Rotational pattern. Here 0 is for clockwise direction and 1 is for anti-clockwise direction. Then „steps‟ will be displayed asking the user to enter the no. of steps (0000-FFFF). Then it will display „Speed‟, asking for the speed (00-FF). After entering the value of rotational motion, steps and speed, the motor will run at the defined rotational motion, no. of steps and speed, and them it will stop. In the program „cts‟ routine controls the motor in continuous Mode and „step‟ routine controls the motor in continuous mode and „step‟ routine controls the Motor in Continuous Mode and „step‟ routine controls the motor in clockwise direction and „anti‟ routine runs it in anticlockwise direction. To display all the different messages corresponding ASCII codes for each message is stored in the lookup table. The program is given below:

Program:

Result:

1. After proper interfacing and execution of the program the User will be asked to choose option „stepper mode (0 or 1)‟. Press „0‟ or „1‟ from keyboard accordingly.

Continuous Mode:Motor will run continuously at the maximum speed and in the clockwise direction

Step Mode:2. The user will be asked to choose the rotation pattern as „rP (0 or 1)‟. Press „0‟ for Clock-wise or „1‟ for anti-clockwise rotation.

2. The motor will run for specified steps, speed and direction.

Viva Questions:

1. What are the internal devices of 8255?
2. What is a programmable peripheral device?
3. What are the information that can be obtained from the status word of 8255?
4. What is stepper motor?
5. What are the different modes of operation of stepper motor?