You receive communications timeouts even though the driver's transaction timeout settting (see below) is set sufficiently high and network is working properly.
For ASComm.NET: Device.TimeoutTransaction property
For ASABTCP ActiveX Control: ASABTCP.TimeoutTrans property
For ASABTCP-OPC Server: Device Transaction Timeout field.
Rockwell Automation processors use overhead time, or background task time, to perform overhead tasks such as responding to a polled communications message request.
The overhead part of the scan is executed after inputs are read, ladder code is executed, and outputs are written.
The A-B tech note G54059311 outlines how to increase the time or bandwidth in the processor available for communications.
1. Visit the Rockwell Automation Support Center website
2. Select 'Get Support Now'
3. Click the 'Knowledgebase' link
4. Login to the Knowledgebase
5. Query for Knowledgebase article ID 25915 (article titled 'Setting the Overhead Time Slice or Increasing Processor Bandwidth for Communications')
6. Follow the instructions for your processor type.