s7-400 - PLC Programming & Automation

Scaling an Analogue Input in STL: The Integer Maths and Where It Overflows

Chart of the product of the raw count and the scale factor against the DINT limit of 2147483647, showing the ceiling at 77672 for a full-scale reading of 27648 and at 65538 for a raw word of 32767, beside the STL statement list in the order that keeps precision

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

Siemens PLC Programming, S7-300 and S7-400 (SIMATIC S5) PLC

by PLC

Communication Modules Communication modules provide data exchange between PLCs and input-output units or between other personal computers. These modules can be operated by direct connection (point to point) or over a network. In a one-to-one connection, the connected processor includes a dual interface. While one computer port is accessed by the programming device, communication is … Read more