Siemens S7-400 Cable Lengths, Segment in the MPI Network, Segment in the PROFIBUS-DP Network

Networking

5.4Cable Lengths

Segment in the MPI Network

In a segment of an MPI network, you can use cable lengths of up to 50 m. This 50 m applies from the first node to the last node in the segment.

Table 5-1 Permitted Cable Length of a Segment in an MPI Network

Transmission Rate	Maximum Cable Length of a Segment (in m)
187.5 Kbps	50
19.2 Kbps	50
12 Mbps	50

Segment in the PROFIBUS-DP Network

In a segment of a PROFIBUS-DP network, the cable length depends on the transmission rate (see Table 5-2). These lengths only apply if you connect a CPU to a PROFIBUS-DP network via an MPI interface configured as a DP interface.

Table 5-2 Permitted Cable Length of a Segment in the PROFIBUS-DP Network Depending on the Transmisson Rate

Transmission Rate	Maximum Cable Length of a Segment (in m)
9.6 to 187.5 Kbps	1000
500 Kbps	400
1.5 Mbps	200
3 to 12 Mbps	100

Longer Cable Lengths

If you have to implement cable lengths which are longer than permissible in one segment, you must interconnect RS 485 repeaters. The maximum possible cable length between two RS 485 repeaters is the same as the cable length of a segment (see Tables 5-1 and 5-2). With these maximum cable lengths, however, note that no other nodes may be situated between the two RS 485 repeaters. You can connect up to ten RS 485 repeaters in series.

Note that you must count an RS 485 repeater as a node of the MPI network in the total number of all nodes to be connected, even if it is not assigned its own

MPI number. The use of RS 485 repeaters reduces the number of nodes.

Automation System S7-400	Hardware and Installation	5-15
A5E00850741-01