Siemens SINUMERIK 840D sl Function Manual page 1015

Example:
Control units with an activated control unit switchover function must be capable of starting up
an 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_ALIVE
The M:N sign of life is a ring counter which is incremented cyclically by the PLC or set to a
value of 1 when it overflows.
Before a control unit issues an online request, it must check the sign of life to establish
whether 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 unit
goes online without request procedure.
Case 2: m_to_n_alive = 0, control unit switchover disabled. Control unit goes online without
request procedure.
Case 3: m_to_n_alive (T0) = m_to_n_alive (T0+1), control unit switchover disabled. Control
unit 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.
Online request interface
DB19 DBW100
Client_Ident
DB19 DBW102
Client_Ident
DB19 DBW104
Client_Ident
DB19 DBB106
HMI type from NETNAMES.INI
Extended Functions
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
19.2 Several Operator Panels on Several NCUs, Distributed Systems
ONL_REQUEST
Control unit would like to go online and use the online request interface. HMI first
writes its Client_Ident as a request.
Bit 8 .. 15: Bus type: MPI 1 or BTSS 2
Bit 0 .. 7: HMI bus address
ONL_CONFIRM.
If the online request interface is not being used by another control unit, the PLC
returns the Client identification as positive acknowledgement.
Bit 8 .. 15: Bus type: MPI 1 or BTSS 2
Bit 0 .. 7: HMI bus address
PAR_CLIENT_IDENT HMI parameter transfer to PLC
Bit 8 .. 15: Bus type: MPI 1 or BTSS 2
Bit 0 .. 7: HMI bus address
PAR_MMC_TYP HMI parameter transfer to PLC
Type properties of the control unit configured in file NETNAMES.INI. Evaluated
by the PLC when MMC is suppressed (server, main/secondary operator panel,
...), see description of file NETNAMES.INI
NC/PLC interface signals (Z2)
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