Elmo DSP 402 User Manual

This document describes the objects and operational modes of the Elmo DSP-based 
motion controller implementation of the CiA DSP 402 protocol. The Elmo Harmonica 
digital servo drive (part of the 

family of

digital servo drives  ) is used as the main 

example in this document. 

Generally, the DSP 402 protocol refers only to the load behavior relating to the operation 
of speed, position, limits and emergencies. It does not deal with control parameters such 
as PI/P, scheduling and feed forward. The motor can be tuned and the plant parameters 
set with the Elmo Composer, which may or may not use this protocol for settings. The 
protocol offers methods in which a profiled reference can be given to the final load. 

  The DSP 402 implementation is applicable to Elmo position unit modes; that is 

UM=4 or UM=5. This is assumed by the Elmo drive itself and it gives no other 
indication. 

The Elmo controller provides a number of different options for setting commands and 
parameters, such as via the binary interpreter, OS interpreter, RS-232 interpreter and user 
programs. When the user works with DSP 402, all relevant motion commands must be 
given through this method only. Other command sources may prevent it from operating 
properly according to the protocol. 

Subsequently modifying controller states, modes and reference parameters using other 
methods may lead to undefined states. For example, in a fault state, a FAULT_RESET 
from the controlword must be given before enabling the motor again. But sending MO=1 
through the OS interpreter may activate the motor and leave the status word of the  
DSP 402 with an undefined status. 

Other command sources are still useful for purposes not covered by the DSP 402 
protocol. Examples include: 

 

Monitoring the states of and inputs to the 

digital servo drive. 

 

Using the Composer to monitor 

digital servo drive behavior through the RS-

232 port while the digital servo drive is under control of the CAN DSP 402 protocol. 

 

Using the user program (or any of the interpreters) to program issues outside the 
range of DSP 402 usage. For example, when the DSP 402 digital output command is 
not used, the digital outputs can be operated freely by a user program. 

The CiA DSP 402 CANopen Device Profile for Drives and Motion Control is used to provide 
drives in a CAN network with an understandable and consistent behavior. The profile is 
built on top of a CAN communication profile, called CANopen, which describes the basic 
communication mechanisms common to all devices in the CAN network. 

CANopen DSP 402 Implementation Guide 

 

 

 

 

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