Applies To:
  • CitectSCADA 1.00 1.01 1.10 1.11 1.20 2.00 2.01 3.00

How do I use the Siemens Protocol? 

The serial drivers PCxI, MCxI, COMxI or COMx may be used.

The CP525 must be set up with the 3964R Procedure and RK 512 Interpreter. The communcation parameters should be 9600/19,200 baud, 8 Data bits, even parity and 1 Stop bit. The CPU must call the SYNCHRON handling block unconditionally in OB20, OB21 and OB22. The SEND ALL and RECEIVE ALL handling block must be called in OB1.

I/O Devices form
Name: User supplied unique name
Number: Network wide I/O device number
Address: 0 (zero)
Protocol: SIEMENS
Port name: Use the "Port name" from the Ports form

Citect.ini option

Status = 1
Read data from D0:0 on startup or when checking for PLC presence. If an error of 0xA, 0xC, 0x14 or no error is returned, the PLC is put online. If status is set to 0 no checking is done.

SiemensBCD = 1
Interpret BCD as timer value. If SiemensBCD is set to 0 then interpret BCD as 4 digit BCD.

Standard citect.ini options

MaxPending = 1
Block = 50 bytes
Retry = 3
Delay = 0
TimeOut = 770 milliseconds (for 4800 baud)
PollTime = 0
WatchTime = 30 seconds


  • SIEMENS.DLL Siemens Driver for windows
  • SIEMENS.DBF Siemens variable template

Data Types

Db:w Data Block Word
Db:w.b Data Block Bit


b is the block number
w is the word number
b is the bit number 00 to 15