Plc Program "Control Unit Switchover - Siemens SINUMERIK 840D sl Function Manual

Several Operator Panels on Several NCUs, Distributed Systems (B3)
2.2 Several operator panel fronts and NCUs with control unit management option
2.2.14

PLC program "Control Unit Switchover"

Introduction
Control unit switchover is an important controlling function in the overall M:N concept:
● The PLC control unit switchover checks the priorities of the requests and the states of the
● The NCU sets signals and evaluates signals required in connection with the control unit
The control unit switchover function is a software package in the toolbox. It is immediately
available with its standard functionality, but can be modified for special applications
according to individual requirements.
Provision is made for two categories of modification:
1. Simple parameterization of standard functionality
2. More fundamental reconfiguring of the control unit switchover function
Reasons for more fundamental (user-specific) reconfiguring can be as follows:
● Suppression strategy which differs from standard functionality
● Operating mode switchover which differs from standard functionality
● Independent handling of override switch for switchover of control unit
● Existence of a 2nd machine control panel on a PCU.
Program structure
The control unit switchover program consists of:
1. FB101/DB101: Online/offline operating mode switchover
2. FB102/DB102: Active/passive operating mode switchover
3. FC103: Machine control panel switchover
Every program section is implemented in a separate function block (FB) or function (FC).
The variables are stored in a separate instance data block (DB) for each FB. The control unit
switchover main program is stored in FB101. FB101 must be called in an organization block
(OB) in order to activate the functions. FB102 and FC103 are called repeatedly in FB101.
MCP switchover
The MCP switchover is not mandatory. It can be enabled or disabled via the FB101/DB101
variable:MSTT_enable. Assignment in the declaration table:
TRUE: MCP switchover is effective.
FALSE: MCP switchover is not effective, no FC103 call
The MCP assigned to the active PCU is always activated. If the operating mode switchover
function is disabled, then the MCP assigned to the last PCU to go online is activated.
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components involved and switches over if necessary.
switchover function.
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
Extended Functions