Hmi Switchover; Suppression - Siemens SINUMERIK 840D sl Function Manual

B3: Several operator panels connected to several NCUs, distributed systems - only 840D sl
2.2 Several operator panel fronts and NCUs with control unit management option
2.2.7

HMI switchover

With the M:N concept, you can change the control unit properties and states configured in
the NETNAMES.INI file during runtime.
For example, the user can intervene in order to
● switch over control units (see Section "Connection and switchover conditions")
● switch over MCPs (see Section "MCP switchover").
A maximum of two control units can be online at the same time on an NCU. A suppression
strategy exists in order to avoid conflict situations (see Section "Suppression").
The HMI properties are configured for each control unit in the NETNAMES.INI file. If a
control unit wants to go online on an NCU via the switchover protocol, its parameters are
passed on to the PLC of the relevant NCU. The PLC program Control Unit Switchover
evaluates the parameters:
● Check suppression conditions
● Switchover if necessary
2.2.8

Suppression

A maximum of two control units can be online on an NCU. If this is the case, and another
PCU/HT6 wants to go online, it must be ensured that no conflicts occur. This is achieved by
means of the suppression algorithm described below.
Sequence
● The PLC sends an offline request to the control unit to be suppressed.
● The control unit returns a positive or negative acknowledgement to the PLC:
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– If the acknowledgement is positive, the control unit is suppressed (see below), it
terminates communication with the NCU and goes into offline mode.
If an MCP is assigned to the PCU, this is deactivated by the PLC.
The integrated MCP is always assigned on the HT6 and is thus also deactivated.
– A negative acknowledgement is output if processes that cannot be interrupted are
running on the control unit, e.g. operation via RS-232 or data transfer between NCU
and PCU. In this case the control unit is not suppressed and remains online.
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Extended Functions