FB120 carries the orange half-circle in the project tree and the block you have open is the one you wrote on Tuesday. On an S7-1500 that symbol is the result of a checksum comparison, not a time stamp comparison, and the manual lists more than a dozen separate checksums behind it. Three of them have … Read more
MOVE_BLK with COUNT := 20 aimed at an ARRAY[1..10] of Real on a CPU 1516-3 PN/DP does not put the CPU in STOP and does not hand you an error in the diagnostics buffer. The enable output drops to 0, and on a box inserted with the editor’s default settings there is no ENO pin … Read more
A snap7 S7-1200 read – plc.db_read(12, 0, 12) against a CPU 1214C – returns twelve bytes on the bench and an exception on the machine, and the difference is two checkboxes in TIA Portal, neither of them on the Pi. python-snap7 3.1.2 talks the S7 protocol to TCP port 102 in pure Python, so there … 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 GET on a CPU 1511 that reads from a CPU 1214C and comes back with ERROR = 1 and STATUS = 8 has almost always been refused by the 1214C, and the 1214C has no code in it to blame. Two settings on the partner decide whether PUT and GET ever return data, and … 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.
Monitor a block on an S7-1500, build a watch table, and work out why a value sits there: modify against force, optimised blocks, and what STOP does.
Get a CPU 1214C into an empty TIA Portal project: read the order number off the front, pick the firmware the bench CPU can take, and set the device name.
The station is an IM 155-6 PN with an ET 200SP F-DI 8x24VDC HF in slot 3, the CPU is a 1515F-2 PN on TIA Portal V17, and the hardware compiles clean with a warning that says the F-module has no valid PROFIsafe address yet. The guard door on channel 2 is wired as two … Read more
A CPU 1515F-2 PN on TIA Portal V17, an ET 200SP station with an F-DI 8x24VDC HF, and channel 2 on it is a guard door. The buffer showed “Channel 2: Short-circuit” last week and the channel passivated; the electrician found a chafed wire in the door loom and repaired it, the buffer now says … Read more
A first SCL block is two statements long – FC10, for a CPU 1516-3 PN/DP – and the first compile of it comes back with four errors and a warning. Every one of them is a ladder habit typed into a language that reads like Pascal, and the compiler is describing each habit accurately, in … Read more
A CU240E-2 PN sits on the PROFINET IO system of a CPU 1516-3 PN/DP with G120 telegram 1 in its device view, the PLC is writing 16#047F to the control word and 8192 to the setpoint, and the motor does not move. Bit 6 of the status word is set. That bit is “switching on … Read more