Configuration of the cyclical data exchange

For communication purposes, the information for the process data image is stored in a table in the logical Modbus address space.

Depending on the version, the controllers offer between 120 and 512 process input/output data for information exchange.

The data exchange is implemented via function codes (FC). The FCs implemented for process data communication and their configuration are described here.

  • UHX25/UHX45
    • Read cyclically: FC3, offset 0
    • Engineering: FC16
    • Write cyclically: FC16
    • Read/write cyclically: FC23, offset 0
    • Unit ID: 0 or 255
    • UHX25A: maximum of 128 process data units
    • UHX45A: maximum of 256 process data units
  • UHX65/UHX85
    • Multi-read: FC3, offset 0
    • Single-write: FC6, offset 0
    • Read/write: FC23, offset 0
    • Unit ID: 0
    • Maximum of 120 process data units