A PROFIBUS RS-485 segment supports up to 32 nodes ("unit loads") without a repeater; beyond that, RS-485 repeaters must be added, and each repeater itself counts as a unit load.

The 32-node limit comes directly from the RS-485 standard, which assumes each transceiver presents one standard unit load. Once you cross that threshold you cascade segments through repeaters: 32 unit loads per segment, up to about ten segments end to end, gives roughly 250 logical devices on a single DP bus. PROFIBUS slave addresses run from 0 to 125 (126 is the factory default, 127 is broadcast), so the practical ceiling is 122 usable slaves plus the masters.

Always count the repeater itself as a unit load on each of its two segments; engineers regularly forget this and overload the last segment with 32 "real" devices plus the repeater port.