The data frame of the motion protocol always contains the following elements.
D-Len (data length) indicates the number of subsequent useful data items including the command byte. The data frame consists of one byte, so that a motion protocol message can consist of maximum 255 data bytes.
The D-Len byte is always followed by the command code consisting of one byte. The command code is followed by the required parameters, if any. If necessary, a ''super command'' is complemented with a ''sub command''.
All commands are immediately acknowledged with a response (acknowledge) when they are received by the module. This response also conforms to the above described data frame format (D-Len, command code, parameters). After the request has been processed successfully, D-Len is always > ''0x02'' or = ''0x01''. If the request was not successful, D-Len is always ''0x02''. The following bytes indicate the cause of the unsuccessful request.
These modules also issue messages if there was not previous request. The format of these ''impulse messages'' also conform to the above data frame. The following events trigger impulse messages.