At 5 Mbps, the SN65HVD21AD supports cable runs up to several hundred feet depending on cable capacitance and termination. The half-duplex architecture means the bus direction must be toggled via the driver enable, so firmware needs to manage the turn-around time after each transmission. For longer distances (above 1000 ft) or higher noise environments, dropping to a lower data rate like 250 kbps extends reach but requires a different transceiver variant.
5 V-only supply — no 3.3 V compatibility
If your system runs a 3.3 V microcontroller, you will need level translation on the logic-side pins or choose a 3.3 V-rated RS-485 transceiver. The 130 mV hysteresis on the receiver inputs helps reject noise on long bus cables, a feature that matters more in industrial environments with motor drives or VFDs nearby.