Siemens SINUMERIK 840D sl Function Manual

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Several Operator Panels on Several NCUs, Distributed Systems (B3)2.8 Cross-NCU user communication, link variablesExtended Functions166 Function Manual, 01/2008, 6FC5397-1BP10-3BA0Number of write elementsThe write elements available for writing to link variables are limited. Their number is definedby the machine data:MD28160 $MC_MM_NUM_LINKVAR_ELEMENTS.If no more write elements are available for an intended write process, alarm 14763 is issued.The set number of write elements only limits the number of write processes that can bewritten in one block.Dynamic response during writeWriting the link variables is immediately completed for the local NCU in the currentinterpolation cycle (in the sequence of commands). If the user does not exceed the numberof possible write processes (can be checked in system variable $A_LINK_TRANS_RATE) inthe current interpolation cycle, all other NCUs will have access to the written information 2interpolation cycles later. If link variables are used exclusively to coordinate the channels ofa multi-channel NCU, they can be written in the same interpolation cycle.NoteThe user (machine manufacturer) must ensure that the time is consistent for larger datablocks that are logically associated with one another. The transmission is word by word. Thedata quantity which can be transferred in the same interpolation cycle is specified in systemvariable $A_LINK_TRANS_RATE (see "System variables of the link memory"). Atransmission can be protected by marking variables of the link memory as semaphores.