Siemens SINUMERIK Series Function Manual

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Z2: NC/PLC interface signals18.2 Distributed systems (B3)Extended Functions850 Function Manual, 03/2013, 6FC5397-1BP40-3BA1HMI data interfacesUser data from/to the HMI are defined on these:● DBB 0-49 control unit 1 interface● DBB 50-99 control unit 2 interfaceThese data and signals are always needed to operate control units.M:N sign-of-life monitoringThis is an additional monitoring function which must not be confused with the HMI sign-of-lifemonitor. For further information, please refer to the relevant signals.In certain operating states, control units with activated M:N switchover (parameterizable inNETNAMES.INI) must be capable of determining from a PLC data whether they need to waitor not before linking up with an NCU.Example:Control units with an activated control unit switchover function must be capable of starting upan NCU without issuing an online request first.Control unit must go online for service-related reasons.The operation is coordinated in the online request interface via data DBW110:M_TO_N_ALIVEThe M:N sign of life is a ring counter which is incremented cyclically by the PLC or set to avalue of 1 when it overflows.Before a control unit issues an online request, it must check the sign of life to establishwhether the M:N switchover is activated in the PLC.Procedure:HMI reads the sign of life at instants T0 and T0 + 1.Case 1: negative acknowledgement for reading process, DB19 does not exist. Control unitgoes online without request procedure.Case 2: m_to_n_alive = 0, control unit switchover disabled. Control unit goes online withoutrequest procedure.Case 3: m_to_n_alive (T0) = m_to_n_alive (T0+1), control unit switchover disabled. Controlunit goes online without request procedure.Case 4: m_to_n_alive (T0) <> m_to_n_alive (T0+1), control unit switchover enabled.Case 1 ... case 3 apply only under special conditions and not in normal operation.