S7-200 CPUs can be configured to work in network communications. A personal computer with the Step7-Micro / Win32 program or a programming device SIMATIC PG740 can be used as a “master device”. The types of network communication that can be implemented are as follows:
Single Master:
A single master device connected to one or several slave device as shown in the image below:
Multiple Master:
A single master device connected to one or more slave devices or other master devices as shown in the following image.
Using a 10 bit modem:
A single master device is connected to one or more other slave devices or other master devices using a 10-bit modem. Only one connection with the S7-200 CPU can be made using this 10-bit modem. For that you need the following components:
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One S7-200 CPU is compatible with a 10-bit modem, namely the model: CPU221, CPU222, CPU224 and CPU226. Other CPUs do not support the use of the 10-bit format.
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Standard RS232 cable for connecting the Personal Computer to a 10-bit full-duplex local modem
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PC / PPI cable (5-switch) to connect the remote modem to the CPU.
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Connect 9 pins to 25 pins if needed.
The following figure shows the use of 10-bit modems in a network with PPI 5-switches:
Using an 11-bit modem:
A single master device is connected to one or more slave devices or other master devices using an 11-bit modem. Most modems on the market don’t support the use of the 11 Bit format.
Depending on the connection of the personal computer to one or more S7-200 CPUs and/or connections to the network, the following components are needed.
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Standard RS232 cable for connecting Personal Computers to 11-bit full-duplex Modems
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PC / PPI cable (4 or 5-switch) to connect the remote modem to the CPU. If a PC / PPI 4-switch cable is used then a null modem adapter is required.
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If a connection is needed with multiple CPUs in the network, a network adapter is needed (PROFIBUS from Siemens)
The following figure shows the use of an 11-bit modem in a network :
Master Network:
The following image shows a configuration of a personal computer that is connected to several S7-200 CPUs. Step7 Micro / Win32 is designed to communicate with one CPU at a time, but the computer can access any CPU on the network alternately. In this picture, the CPU can be a master or slave while the TD200 is a master.
Network Repeaters:
This network repeater is needed if the distance between the CPUs is far apart if you want to add a CPU, or to isolate a network from another network. PROFIBUS can connect 32 components in a network within a distance of up to 1200m.
A repeater will allow the addition of 32 more components and an additional distance of 1200m at the 9600 Baud rate. In the network, 9 repeaters can be used with a network length of no more than 9600m. Each repeater will provide Bias and Termination for each network segment.
