Re: [foxboro] FBM231 modbus with siemens

Try the following things:

- to use another modbus slave (such as an analyzer) and see if the =
problem
persists.
- use a modbus simulator to read and write coils and registers to the
siemens plc...as said in another post, the siemens plc uses custom =
blocks
and functios installed on the cp's to perform modbus comunications. =
Since it
is not a standar for siemens, there might be some limitations regarding
modbus functios
- to read and write only one register at a time. If this works, then
increase the data being requested by little increments.
- take a look on how many bytes are you sending and requesting, try to =
limit
the byte quantity to no more than 100 bytes
- try to establish a poll frequency for no less than a second, i guess =
500
msec is to high (it depends on the physicall link, indeed)

if you dont have a modbus simulator i can send you one.

good luck


Gonzalo Diaz
Mantenimiento Planta LPG
Servicios Buproneu S.A. (Capex S.A.)
Yacimiento "Agua del Caj=F3n"

-----Mensaje original-----
De: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] =
En
nombre de FoxPat
Enviado el: Jueves, 18 de Octubre de 2007 14:14
Para: foxboro@xxxxxxxxxxxxx
Asunto: [foxboro] FBM231 modbus with siemens

Dear list,
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We're having some problems with a new modbus link.

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FBM231, modbus driver version 1.1, scan-rate 0.5 seconds.

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Reading coils and registers is no problem.

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Writing coils works but after a certain amount of writes (just toggle of =
1
BOUT) the complete link starts to fail intermittently (works for a few
seconds and then all smurfed for a few seconds, works again for a few
seconds, smurfs .. Etc).

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Only a reset of the Siemens communication card (pull-push, there's no =
reset
button) solves the problem, but after several write attempts fails =
again.

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Installed all the DCI IIN blocks for FBM port and device counters (as
described in the manual) but these don't help me much other then =
indicate
there are no CRC or framing errors. Scan time is only about 100 mSec.=20

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I hope to install a modbus analyser tomorrow to see what is actually
happening.

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Anybody had similar problems?

Any suggestions ?

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=20

Kind regards,

=20

Patrick Martens

Total Refinery Nederlands. N.V.

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