I recently discovered that when downloading an online edit [S7-1500] that requires the initialization of the modified FB's iDB, an IEC timer whose input [enable] conditions are already at logic 1 will reset its output but not re-trigger and run because it hasn't seen a 0/1 transition at the input through the download. Siemens tech tell me that this is because the DB and FB are loaded simultaneously and that there's no way around it without external logic to break the input to the timer when the download takes place.
Today I had to cycle the power to the processor and the same thing happened when it came back on: all timers with pre-existing enables didn't restart. In my application, they're all on-delay debounces for level control thresholds, so all the pumps that should have restarted didn't. This response suggests that I won't be able to create a universal TON instruction or pulse timer at the top of the program to generate a reset pulse if that timer is unconditionally enabled, as I would in A.B.
Can anyone help me out with this one? Thanks.
Today I had to cycle the power to the processor and the same thing happened when it came back on: all timers with pre-existing enables didn't restart. In my application, they're all on-delay debounces for level control thresholds, so all the pumps that should have restarted didn't. This response suggests that I won't be able to create a universal TON instruction or pulse timer at the top of the program to generate a reset pulse if that timer is unconditionally enabled, as I would in A.B.
Can anyone help me out with this one? Thanks.