IEC/TR 61491:2010 presents an overview and guidance for IEC 61158, IEC 61784-1, IEC 61784-2 and IEC 61800-7 with respect to a real-time serial interface between the control unit and its associated devices, which is utilized to transmit periodic and non periodic data. This interface is intended to apply to industrial machines, such as machine tools, with multiple devices connected via this interface. This interface supports different operation modes. This first edition of the technical report cancels and replaces the second edition of IEC 61491, published in 2002. The changes are primarily to make reference to material that was moved to IEC 61158, IEC 61784 and IEC 61800-7 series of standards.