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 Post subject: Alarm server using too much bandwidth
PostPosted: Wed Feb 20, 2013 10:45 pm 

Joined: Wed Feb 20, 2013 10:32 pm
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Hello,

We have 16 controllers, each with two 24 bit registers corresponding to a total of 768 tags monitored by the alarm server. We can add about 1/3 of the tags to the alarm server before we get com errors.

Communication: modbus ascii over rs232
timeout: 400ms
They are all on poll group 1 at 400ms. This is about the max, or other buttons seem slow for other functions.

Will separating them into different poll groups stagger the requests over modbus? Is there any other way to help space out the requests coming from the alarm server?

Thanks. --Karl


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 Post subject: Re: Alarm server using too much bandwidth
PostPosted: Thu Feb 21, 2013 9:13 am 

Joined: Tue Mar 13, 2012 9:53 am
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Can you increase the serial port baud rate? It defaults to 9600 in iX Developer. It sounds like you are trying to push more data through the serial cable than it can handle.

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Best Regards,
Mark Monroe

Beijer Electronics, Inc. | Applications Engineer


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 Post subject: Re: Alarm server using too much bandwidth
PostPosted: Thu Feb 21, 2013 9:54 am 

Joined: Wed Feb 20, 2013 10:32 pm
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Hello, Thank for the fast reply. Yes, we a re running at 115,200 baud. --Karl


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 Post subject: Re: Alarm server using too much bandwidth
PostPosted: Thu Feb 21, 2013 11:00 am 

Joined: Tue Mar 13, 2012 9:53 am
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You could try increasing the "Max Block size (words)" to 60 or more in the Controller settings and see if you get any errors. The larger the blocks, the more efficient the communication. However, not all Modbus Slaves can handle large block sizes, so you may start to get error is you increase it to much.

Besides the poll rate, there is no other way to change the polling frequency.

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Mark Monroe

Beijer Electronics, Inc. | Applications Engineer


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