A Modbus RTU bus on RS-485 supports up to 32 nodes per segment (extendable with repeaters), requires 120 ohm termination resistors at both ends of the bus, and biasing resistors to define the idle state.
True
The RS-485 standard natively supports 32 nodes per segment using "1 unit load" drivers, and up to 128 or 256 with modern "1/4 unit load" drivers. 120 ohm terminations are required at both ends of the bus (unlike KNX TP1) to match line impedance and prevent reflections. Pull-up/pull-down biasing resistors (typically 680 ohm to 1 k-ohm), usually placed at the master, hold the idle state stable when no node is transmitting. The recommended cable is a shielded twisted-pair with 120 ohm characteristic impedance, and the maximum length is around 1200 m at 9600 baud (less at higher data rates).
If you only ever remember three numbers for an RS-485 audit, make them 120 (termination ohms), 32 (nodes) and 1200 (metres at 9600 baud).
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