On an S7-1200 or an S7-1500 there are four places a function block can keep state that is not in its instance DB, and every one of them makes a second FB instance of FB_Valve share memory with the first. The report is always one of three: valve 2 opens when valve 1 is commanded, … Read more
What a Studio 5000 alias tag shares with its base, how it changes a force and a cross reference, and the tag scheme an alias cannot fix on a 1756-IB16.
Find every instruction that writes a tag in Studio 5000, tell a write from a read, and work out why an output with two writers flickers on a 1756-OB16D.
Zone 6’s eye came out of stores as a 42EF-P2KBB-F4, went onto the bracket in place of a 42EF-P2JBB-F4, and from the next 600 mm carton on, zone 6 reported occupied while it was empty and empty while a carton stood on it. One letter in the fifth position of the catalogue number, K for … Read more
A know-how protected OEM block will not open. What TIA Portal still lets you do with it, why the compile error sits in your call, and how to clear it.
An S7-1500 area length error leaves the CPU in RUN with the ERROR LED on. Read the buffer entry, find the index that runs past the array, fix the order.
A TON with a .PRE of 5000 that sits in a subroutine only called in Auto, with its rung left true, is already done on the first scan back after twenty minutes in Manual. Publication 1756-RM018A-EN-P prints the arithmetic that explains it, ACC = ACC + (current_time – last_time_scanned), so the timer bills the whole … Read more
A repeatable PLC troubleshooting order: module LEDs, controller major faults, I/O connection status, forces, cross-reference, trends and Ethernet checks.
Build watch lists in the Studio 5000 Watch window, monitor and write tag values online, and know when the sample rate hides what you are chasing.
A rung by rung ControlLogix ladder troubleshooting method: read the highlighting, use cross reference and search, find double coils, read the fault record.