Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 60

Configuring
4.11 Planning subnets
Longer cable lengths via RS 485 repeater
You need to install RS485 repeaters for segments requiring cable lengths longer than the
allowed length. For further information, refer to the RS485 Repeater Product Information.
Stub cables
Make allowances for the maximum stub cable length when you connect bus nodes to a bus
segment by means of stub cables, for example, a PG via standard PG cable.
For transmission rates up to 3 Mbps, you can use a PROFIBUS bus cable with bus
connector as stub cable. For transmission rates higher than 3 Mbps, use the patch cord to
connect the PG or PC. You can connect several PG patch cords to the the bus (for order
numbers see table 4-20). Other types of stub cables are not permitted.
Length of stub cables
The table below shows the maximum permitted lengths of stub cables per segment:
Table 4-19
Transmission rate
9.6 kbps to 93.75 kbps
187.5 kbps
500 kbps
1.5 Mbps
3 Mbps to 12 Mbps
To connect PGs or PCs when operating at rates higher than 3 Mbps, use patch cords with
1
the order no. 6ES7 901-4BD00-0XA0. In your bus configuration, you can use multiple PG
patch cords with this order number. Other types of stub cables are not permitted.
PG patch cord
Table 4-20
Type
PG patch cord
4-36
Lengths of stub cables per segment
Max. length of stub
cables per segment
96 m
75 m
30 m
10 m
1
PG patch cord
Number of nodes with stub cable length of ...
1.5 m or 1.6 m
32
32
20
6
1
Order number
6ES7 901-4BD00-0XA0
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
3 m
32
25
10
3
1