As the distances between nodes in an RS-485 network become greater and greater, it becomes more of a challenge to ensure reliable communication. The increased distance often means that the reference (ground) potentials has more of a difference between nodes. These ground potential differences give rise to differences in the common-mode voltages seen by the various transceivers on the bus. Standard RS-485 transceivers are typically specified to operate over a common-mode voltage from –7 V to 12 V, which may be insufficient for larger distances. The SN65HVD2x family of devices extends this range to –20 V to 25 V, allowing for greater communication distances between nodes.

Increased cable lengths can lead to increased jitter, especially in links operating at high data rates. This increased jitter is due to the attenuation of the cable, which tends to increase with frequency. Having unequal loss between higher and lower frequencies causes the RS-485 signal to distort, adding some timing deviation (jitter) to the edge crossings of the RS-485 data. If the jitter amplitude exceeds the jitter tolerance of the receiving MCU or UART, then bit errors are likely to result in the link. However, jitter can be reduced for a given link through the use of receiver equalization.