from the Project Engineer on mothers side department...
Siemens HMI OP7
PLCs and related questions. topic
Posted by Ken on 5 November, 2002 - 8:14 am
I am new to Siemens programming and trying to learn how to program the OP7 HMI. I have not yet managed to find a straight forward programming manual for the OP7. I have looked at all the files on Protool V6.0+ Service Pack 1, but have not been successful.
I have managed to down load a program to the OP7 HMI, but are now getting a message saying:
$551 AS address 2 not possible

I then amended my program and tried to down load it again: E4027: Synchronization faulty
No connection to the OP!
I think I have to set the OP7 to Download mode by press a number of keys, but have not yet found this information.

Please could anyone help me!!!

Posted by Nilesh Patel on 5 November, 2002 - 12:44 pm
Hi Ken,

You may find more info. about your problem on website "": which is dedicated to siemens PLC.

Or you can contact to owener of
(Luca Genilla), He will help you more on that point.


Posted by Ken Barry on 5 November, 2002 - 5:14 pm
Hi Nilesh,

Thank you for your reply, I will try the
website "":



Posted by Colin on 7 November, 2002 - 9:37 am
I have a manual for the OP 7 in pdf format, if you send me an E-mail (cfradd(AT) i will send it back to you but this is what it says about fault 551..An MPI/PPI connection to the PLC cannot be established using the specified station address. Check MPI station addresses and wiring. I hope this helps.


Posted by Gabriele Corrieri on 7 November, 2002 - 4:02 pm
Hi Ken

Error message
$551 AS address 2 not possible

is meaning that MPI, or PTP, or DP, or in every case connection plc-op is faulty.

This depends basically by 3 factors:

a)connection cable (A and B reversed is common error)

b)terminating resistors at each end of bus

c)the cpu connected doesn't have address 2

I suggest you to unplug connection cable, and check with ohmmeter from A to B that is 110 ohm, if is 220 one resistor is open, if is open both resistors are open, please switch the termination at ends to ON, and the connector between to OFF (if there is any).

Check cpu address, and reversing A-B wires into connectors.

If you have other question you can freely contact me.

Gabriele Corrieri

Posted by sameer on 18 November, 2002 - 10:24 am
Hi Ken,
such an error message is possible only when the connection is not made properly .ensure that the port of your PLC is properly connected with OP7 .The terminal connections and pin details can be taken from the manual of s7-200 and can obtain the manual of s7-200 from siemens



Posted by vivek on 19 April, 2008 - 4:07 am
Redundancy means you require two CPUs with distributed I/O module systems. You go for Siemens S7-400. Prolific is counducting detailed training program on Siemens OP7. If you require detailed practical exposure please write an e-mail to pune @ prolifictraining. com

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