Siemens SIMATIC NET PROFIBUS manual Rules

Configuring Networks

Rules

At a transmission rate of 1.5 Mbps, the following rules apply to the permitted number of nodes and their distribution/layout on a SIMATIC NET PROFIBUS segment:

1.The maximum permitted number of nodes on any segment is 32.

2.The sum of the values of all the connection elements in a segment must be

≤25.

3.The rules for the distance between adjacent connection elements are as follows (distance in this case is the length of the LAN cable):

3.1If the distance between adjacent connection elements is greater than 10 m, the values of the connection elements can be ignored.

3.2If the distance between adjacent connections elements is greater than the sum of the two values of the elements in meters, the layout is not critical and no additional conditions need to be taken into account.

The value of the PG connecting cable, SIMATIC S5/S7 connecting cable 12 Mbps must be added to the value of the corresponding connection element.

3.3If the minimum clearance described in 3.2 is not kept to, this results in

a group being formed and the following additional conditions must be met:

–Attachment elements can be arranged as close to each other as required providing the sum of their values does not exceed the value 5.

–The distance in meters between two adjacent groups must be at least as large as the sum of the values of the two groups.

3-6	PROFIBUS Networks SIMATIC NET
	6GK1970-5CA20-0AA1 Release 2 05/2000