In my application Modbus protocol mbread block is used. After online download, some mbreadblock are stuck. In attached image, Enable is true but still status 65534.
After manually clearing i_state current value 100 to 0, it started working normally.
What could be the cause ? It happened 2 times after performing online download.
I would make sure the blocks are being disabled during the transfer. I would use the PROGRAM _EXIT block to call the blocks with enable = 0 until you get the status to be 65534 (Enable False).
What is likely happening is there is a memory shift during the transfer (especially if it is a change to this task), and the block is still trying to call the function block on the data at the old area of memory.
Hi Matt,
Thanks for the feedback. In our application it is Serial Device connected on TCP Gateway, so we are using Incremental counter to Enable each mbread on suncessful read done [ status Value 0] or Error [ Status Value > 0 < 65534]. For eg in our application we have FB each with 10 mbread. 5 FBs above are incrementing properly, when it comes to 6th FB 4 mbreads are ok and get stuck in 5th mbread. 6th mbreadblock could not executed since mbreadblock5 does not generate Done or Error status. and rest of FB after this are not executing. Will be of great help to get a sample modbus rtu application.