Siemens Simatic S7-300 CPU 31xC Series User Manual

Configuring
4.11 Planning subnets
S7-300, CPU 31xC and CPU 31x: Installation
4-36 Operating Instructions, Edition 08/2004, A5E00105492-05
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 Lengths of stub cables per segment
Number of nodes with stub cable length of ...
Transmission rate Max. length of stub
cables per segment
1.5 m or 1.6 m 3 m
9.6 kbps to 93.75 kbps 96 m 32 32
187.5 kbps 75 m 32 25
500 kbps 30 m 20 10
1.5 Mbps 10 m 6 3
3 Mbps to 12 Mbps
1 1 1
1
To connect PGs or PCs when operating at rates higher than 3 Mbps, use patch cords with
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 PG patch cord
Type Order number
PG patch cord 6ES7 901-4BD00-0XA0

Siemens Simatic S7-300 CPU 31xC Series Specifications

General

Series	S7-300 CPU 31xC
Power Supply	24 V DC
Communication Interfaces	MPI, PROFIBUS DP
Programming Languages	LAD, STL, FBD, SCL
Operating Temperature	0°C to +60°C
Memory	48 KB - 512 KB
Dimensions	40 x 125 x 130 mm (varies by model)