Siemens S7 & Citect V5.42 ethernet

First of all Hi everyone,

I'm trying to comunicate a Siemens S7400 with a Citect and the values on the screen sometimes are switching among the value a the "#com" message.
Seems that sometimes is loosing the communication ???!!!
Om the Citect's syslog file appears values like:

Tue Oct 09 13:15:01 2007 03:46:53.374 Error: General error
READ 0008 PORT_TANKS IOREACTORS DB344,REAL966,15 60
Generic 000008 Driver 00008200 (0x00002008)

The tag seems to be right defined on the PLC and also on the Scada ??...

Anyone got any idea ??

Thanks in advance...

Icapa.

Don't know if you have access to the knowledge base but if you look at article Q3634 there is the explanation of your problem.

#COM on only some Tags of type REAL via the S7NT Driver

Article number: Q3634
Updated on: 21/05/2004
Product: Citect for Windows Versions

[size=+]Summary[/size]
Sections of PLC datablocks and whole datablock values being read by Citect are coming up with #COM errors. Other data blocks in the PLC are being read OK.

Occasionally on some pages where some of the #COM values in one of the blocks are being displayed, a value will be seen for a moment, and then go back to #COM status.

Error Message in Citect Hardware Alarms: "2008 - Not in Database"

[size=+]Solution[/size]
The actual error message for 0x2008 is "ILLEGAL REAL VALUE"

There are a number of possibilities for this;

1. Within the data block the real tags must fall on 4 byte boundaries. This is explained in detail in the driver specification document, (sseven.pdf, Page 18, section 5.13 b)

2. The PLC has a value in one (or more) of the registers being read by Citect that is outside the IEEE REAL format -3.402 823E+38 to -1.175 495E-38 and 0 and +1.175 495E-38 to +3.402 823E+38, which is used by Citect. With the Siemens S7-400 / S7-300 some operations may create an invalid range for the result, however it will set a combination of bits in the status word when this occurs (the bits are CC1, CC0, OV, OS).

For REAL types that are read by Citect you should use the status bits to correct the result.


Regards,

Marsupilami

HI,

The format shouldn't be a problem.... the TAG is defined on the PLC as a REAL type on the DB, so is using 4 byte, and the value is also into the ranges allowed....
DB344.966 REAL
The value shown in REAL format is 6329,572
The value shown in Float format is +6.330e+003

The DB where I have the REAL values is a DB that have the values from the analog Inputs and I use a UDT structure that is using all the analogs. So I can't understant why some displayed values show the "#COM" and why someones not. If I have the same UDT structure for all of them, all should have the same problem if it was a structure problem.

REading some more articles from the knowledge base I've seen the Q3848 where is described...
This is my case??.... on the Siemens UDT structure I'm using I have INTs and REALS.
I'f tested to set the EnableFloatCheck to 0 and the error does not appear anymore on the Syslog.dat !!!...but still have the "#COM" on the display !!!!!

UFFF....

I'm still playing with it... but I will apreciate some help if someone have the solution.

Thaks a lot.

Are your addresses of your Real tags dividable by 4?

So DB100,100 would be OK since 100/4 = 25
but DB100,102 would be incorrect.

In any case, mixing of types is never a good idea when using the S7NT driver. If you look in the help topic "S7-300 & S7-400 PLC - MPI: Hints & Tips" it is explained why.

Grouping you tag by type will also improve your performance.

another option is to use the PS-Direct driver but you will have to buy it seperatly. But you save on the costs of Simatic Net. Be careful the PS-Direct driver is not always an option.

Regards,

Marsupilami

Hi,

You're mate the REAL value must be on a DBDxxx divisible by four !!!!
Doesn't matter if you have in the middle BOOL, WORD, INT... values also on the DB, the only condition is that REAL have to be on a position divisible by 4.

What a F#@#K S@#T of scada !!

Thaks Marsupilami for your help.