Knowledge Base

A system may contain up to 32 RS485 devices on one pair of wires. Typically distances of many 100’s of metres can be realised with RS485, and with the relatively low data rate of Xwire (38.4 Kbaud), performance of the connecting wires is relaxed. It is impossible to actually specify the maximum distance over which reliable data transfer can be achieved, as there are unknowns that affect the performance, such as the amount of electrical noise and the connecting cables electrical characteristics.

Also, to minimise ground currents through the 0V connection, it is advisable to either have the controllers and Xwire peripherals all isolated from mains earth, or to only ground one controller at one location (usually the Xwire master). The X485 is fitted with transient suppression diodes to prevent damage due to strong electrical noise on the A and B data lines.