Topology

• A bus segment may consist of a maximum of 32 devices (including the repeaters).
• The maximum conductor length of a segment depends on the transmission speed in use and on the quality of the bus cables being used.
• No more than 9 repeaters may be installed between two devices.
• Stubs are to be avoided, and are not permitted above 1.5 Mbaud.
• The maximum number of devices is 127
• Interrupting the supply voltage from cable ends by switching off the repeater/slave, or by pulling out the plug, is not permitted.

Fig. 1: RS485 topology with 3 segments and 2 repeaters.