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Change axis positive/negative motion direction

In some applications it may be desirable or necessary to change the controllers sense of positive and negative direction for an axis. The following methods will change both the commanded direction and encoder direction for an axis. These commands do not change the assignment of positive and negative home sensors, so these may need to be rewired.

Set the Invert Motion Direction Flag bit 8455. Requires FLASH SAVE or FLASH IMAGE command to retain setting after power cycle.


  • The Invert Motion Direction Flag is not part of the configuration wizard but could be added to the Defines or a PBOOT program that initializes application settings.
  • SET or CLR of the Invert Motion flag is only allowed while the Drive is off/disabled for the axis. NOT VALID WHILE DRIVE ENABLED error will result if SET or CLR is issued while the drive is enabled. If the error occurs in a running program, that program will HALT automatically.
For a DAC axis the Invert Motion Direction flag will invert the sign of both MULT and DAC GAIN. Each time you SET this bit, these values are multiplied by -1. Recommend instead setting DAC GAIN and MULT explicitly somewhere in code to the needed settings.

For applications using the secondary encoder input, its direction can be changed with the MULT command.



Change the sign of the encoder multiplier:

Issue ESAVE to retain these value after power cycle.


  • The Configuration Wizard will always set these values to DAC GAIN 3276.8 and MULT 4. If the direction needs to change, the modified commands must be issued after a configuration download. Consider adding to the Defines file or a PBOOT program that initializes other application settings.
  • The Servo Tuner and Jog/Home dialogs included in the Configuration Wizard will resend the default settings. Avoid these dialogs after making direction changes. If needed, use the Servo Tuner and Jog/Teach panel locate under Tools in the ACR-View project workspace.
  • With some drive/motor combinations, the command direction (DAC GAIN) and encoder direction (MULT) may need to be different. For Example DAC0 GAIN 3276.8 and ENC0 MULT-4. Use caution when making this type of change as it could result in a runaway condition.