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[KB48]Maximum number of pending Write requests

Tags: Cimway, Modbus TCP/IP

Data acquisition
14 years ago
By RM
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Applies to:

PcVue version 7.20d onwards.
While the basic content of this article remains valid, details may have changed since it was written.
Summary:

This article explains how to configure an upper limit on the number of pending frame writes.
Details:

The maximum number of write requests is configured as follows:

  • Select the menu Configure.Project.General Operation to open the General Operation Configuration dialog.

Gen_Op_Config_dlg_Max_Pending_Frames

  • In its Communication folder, open the subfolder Maximum Number of Pending Frames… and click on the value in it to open the dialog Maximum Number of Pending Frames…

Gen_Op_Max_Pending_Frames_dialog

  • Adjust the setting of ‘Maximum number of pending frame writes’. The default value is 100.
  • Click on OK to close the dialog.

Messages

Warn

A write request will be rejected if the number of writes queued is 10 times the configured limit.

The following message appears in the Event Viewer when the maximum number of pending write commands is reached (100 by default, as above).

…,I,…CW,4535,, Too many pending write command

When the maximum number of pending write commands reaches 1,000, another message appears in the Event Viewer.

…,…,I,,4578, ,1,CW, Number of write requests in progress is too high (Nack)

Write command requests will be rejected to avoid stack overflow.

You must then modify your project to reduce the number of write commands using the SCADA Basic instruction SET/SENDLIST .

 

Created on: 08 Oct 2010 Last update: 13 May 2024