COP and CPS Instructions on a ControlLogix: Which One Copies What A COP with a Length of 20 moved five bytes. The source was Packer_Raw, a SINT[5]; the destination was Packer_Scaled, a DINT[10]; the rung went true on every scan of a 1756-L71 and nothing faulted, nothing latched, nothing appeared in the Minor Faults tab. … Read more
The bagger came back with 0.0 in every recipe setpoint at 06:10, with nobody at the HMI and no download on the log. The only change on that shift was a program that had been inhibited while somebody edited it and then put back in, and the initialisation rung inside it — one XIC on … Read more
Line 2’s palletiser infeed stops about once a shift with Infeed_Jam latched, the alarm log says “Infeed jam” with a time, and the 1756-L83E, the PowerFlex 525 and the 1756-IB16 feeding the discharge photo-eye all check out every time somebody looks. Whatever happens takes a few tens of milliseconds and happens hours apart, and the … Read more
At 02:30 on Sunday 25 October 2026 a logger in Berlin writes a row, and sixty minutes later it writes another row stamped 02:30, and the trend viewer draws the second hour on top of the first. Meanwhile the controller it reads from keeps its own idea of the time as a LINT of microseconds … Read more
A spare CPU firmware mismatch looks like this: a new 1756-L83E ships at firmware revision 1.xxx, and a project saved from Logix Designer v33 will not download to it until the controller is at some 33.xxx. Those two facts sit on the same page of the ControlLogix 5580 user manual, and between them they are … Read more
A UDT holding a STRING, eight REALs, four DINTs and four BOOLs is 140 bytes, and the Data Type Editor in Studio 5000 prints that number under Data Type Size before you have written a rung. Fifty of them in a PLC recipe UDT array is 7000 bytes and one base tag, and that last … Read more
Siemens gives you a Retain checkbox and a published memory budget. Rockwell gives you neither. Here is what each one really keeps, and how to check it.
Read process gain, dead time and time constant off one bump test, then enter them in the units PIDE actually wants instead of the ones the PID wants.
Pick between TON, TOF and RTO, find out what retentive actually covers on each platform, and stop losing an afternoon to a timer that never times out.
Store a ControlLogix project to a 1784-SD2 card, pick the Load Image setting you need, and what an upload or a card restore will not give back at 3am.
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.