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 CPU 315-2 PN/DP with 6ES7315-2EH14-0AB0 on the label maps to a CPU 1515-2 PN, 6ES7515-2AM01-0AB0, in the Siemens migration guide’s CPU table, and the S7-1500 migration does not happen in one move. It happens in two, the second of which is a right-click on the old CPU in the device view called Migrate to … Read more
Step 2 of a two-step TIA Portal GRAPH sequencer on a CPU 1515-2 PN has been active for 4 minutes 12 seconds by its own S2.T, the transition below it has been satisfied for the last 40 of those seconds, and the sequencer is still sitting on step 2. The heater that step 2 drives … Read more
Zone 3 of the takeaway conveyor stops about once a shift with “Zone3”.Fault latched, the photo-eye on %I4.3 reads a steady 1 in every watch table anybody has opened, and the CPU 1516-3 PN/DP is turning OB1 over in about 6 ms. Whatever is happening is happening inside one of those 6 ms passes, hours … Read more
A Pt100 RTD input wired two-wire over 22 m of 0.5 mm² cable into channel 0 of a 1756-IR6I reads 104.1 °C in a bath that the reference thermometer says is 100.0 °C, and the same sensor with its third lead landed on RTN-0/C reads 100.0 °C. Lift lead A off the module and the … Read more
A CPU 1516-3 PN/DP in RUN on the filler, a SIMATIC memory card behind its front flap, and no project file on any laptop in the building. An S7-1500 upload – online, Upload device as new station (hardware and software) – and about three minutes later an empty project holds the rack, every block with … Read more
A DINT stops at 2147483647, and 27648 multiplied by 77673 is 2147503104. That is the whole of the problem with fixed-point scaling in STL: the arithmetic is exact right up to the statement where it is not, and *D reports the crossing by setting OV and OS rather than by refusing to run. Here is … Read more
On an S7-1500 a 4 to 20 mA channel reads 0 counts at 4 mA and 27648 counts at 20 mA, and a channel with wire-break diagnostics enabled reads 32767 when the loop opens. Those three numbers decide the rest of this page: what goes in the MIN and MAX pins of NORM_X, what SCALE_X … Read more
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.
How functional safety works on a PLC job: the ISO 13849-1 risk graph, PLr, category 3 architecture, MTTFd, DC, CCF, a PFHd budget and SISTEMA.
Add one Static to an FB and every setpoint in the instance DB goes to zero. How the memory reserve prevents it, how to size it, and how to recover.
What is in a PLC rack and how the software sees it: power supply budget, CPU memory, I/O cards, tasks and routines, and tags against S7 addresses.