RS-485 bus survival — what the ratings mean
The MAX491ESD+T: 2.5 Mbps data rate is the switching ceiling — on a long stub or unterminated drop, the signal edge slows and the bit-error rate climbs before you hit that number. Keep the bus properly terminated and the stub length under a few inches to hold the full rate. 70 mV of receiver hysteresis filters out noise on a floating or lightly loaded bus — that is enough margin to avoid chatter on a 100-meter run in a factory with VFD hash on the ground plane.
Industrial temperature and bus fault tolerance
Full-duplex means the driver and receiver are active simultaneously — you get a dedicated pair for TX and a pair for RX, which halves the cable count compared to half-duplex on a two-wire bus. The node count on a single segment is limited by the driver's load capability, not the protocol.