hello

i have cnc 5 axis with  siemens 840d powerline system .

In one of plc BLOCk we have 

NETWORK 26

  A     DB157.DBX   40.0
     =     DB145.DBX   27.0
     A     DB200.DBX   30.4
     =     DB145.DBX   27.1
     A     DB157.DBX   40.1
     =     DB145.DBX   27.2

NETWORK 27
      CALL  FC    21
      Enable :=TRUE
      Funct  :=B#16#4
      S7Var  :=P#DB145.DBX 24.0 WORD 4
      IVAR1  :=240
      IVAR2  :=238
      Error  :=DB145.DBX18.1
      ErrCode:=DB145.DBW22
 

In  my user programme $A_DBB [242 ] corresponds to DB145.DBb 27 . It is only possible if in  FC 21 ivar 1 =240  corresponds to  $A_ DBB[239]. 

i have other doubt - in user programme they are using semaphore byte $a_dbb[238]=0. why it is being set to zero?

 

 Thank you nulizhang .

Sorry for late reply.

Got it . Data field ia specified by byte offsef.. and we need to set the semaphore byte for dafa consistency.

nulizhang

 Suggest you to read  "Siemens 840D powerline function manual Basic FB1"  section 2.12.5 for  FC21 --I attach here for you