Industry Online Support
Technical Forum
6/5/2008 9:21 PM | |
Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (308) |
Hello, 1) You will constantbus cycle times if your process requires constantupdates without jitter. Some examples are fast PID controllers using distributed analogue values, or the coordinatedspeed control of drives, ... If you try to control a fast process value and you do not compute each update of the control value with real values coming equidistant in time, the control will not be accurate. More details in this manual: http://support.automation.siemens.com/WW/view/en/15218045 2) In a single Master bus with pure I/O devices, the time needed to scan each device will be fairly constant. Butat certain intervals the Master will for instance also checkif new devices are willing to enter in the Token distribution. This gives already a certain variation. In a multi master bus (several PLCs, or a PLC with a PG on the bus,or with a HMI on the bus)the overalll bus cyclewill alsovary depending on theactivity of the diagnostic device on the bus (PG), orthe amount of data read by an HMIconnected on the bus (depending on screen changes,...),... |
Best regards |
|
6/5/2008 11:24 PM | |
Posts: 5822 Rating: (412)
|
Hello, just one thing, the parameters calculated in STEP7 for example are worst case values, the Bus is usually always faster than that. Best regards J_Bell |
Follow us on