Siemens SIMATIC NET PROFIBUS Owner's Manual page 76

Configuring Networks
Configuring
When configuring an electrical network with RS-485 repeaters, the following
conditions must be taken into account:
S The maximum segment length for the transmission rate must be adhered to
(see Table 3-1, Table 3-3, Table 3-6,)
S The maximum number of bus attachments (nodes, OLMs, RS-485 repeaters,...)
in one segment is restricted to 32. There may be further restrictions at a
transmission rate of 1.5 Mbps (see Section 3.1.2).
S The maximum number of nodes in one network is limited to 127.
S A maximum of 9 RS-485 repeaters can be installed between two nodes.
3-10
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000