8/15/2014 11:07 AM | |
Joined: 11/29/2011 Last visit: 8/19/2024 Posts: 1359 Rating: (232) |
Hi, Substitute Values When your PLC start up, the cards do not get Proccess image updates from the CPU untill the first valid OB execution. (There is a way to access the peripherial IO from the startupOB directly but it is a lot of extra effort and it can extened the startup time) The first PIP update arrive with the first exectuation of the relevant OB. Between the full download and the first normal OB execution, the cards recieve their config data (including substitute value) and wait for theprocess image update.As they do not get valid transmition for a few seconds they apply the substitute value. My recomendation is check your HW config for substitute values first. Make sure that all your card configured to bring the outputs in the safe state in the case of loss of communication. Read below ion chapter 27.1.3. under Sequence of activities: http://support.automation.siemens.com/WW/view/en/45531107 Cheers |
Last edited by: MicroMan at: 8/15/2014 11:08 AMI assume your cards support substitute values. - What you read here, please check with manuals and your requirements. |
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