Siemens CPU 312C

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S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
5-32 A5E00105492-03
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These subnets are the most frequently used for S7-300 CPUs, so they are
discussed in detail below.
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In the following, all networked devices are referred to as nodes.
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A segment is a bus link between two terminating resistors. A segment can include
up to 32 nodes. It is also limited by the permitted line length, depending on the
transmission rate.
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These maximum transmission rates are possible:
• MPI
– CPU 317-2 DP: 12 Mbps
– All other CPUs: 187.5 Kbps
• PROFIBUS DP: 12 Mbps
• PtP:
– Half duplex: 38.4 Kbps
– Full duplex: 19.2 Kbps
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Maximum possible number of nodes per subnet:
Table 5-13 Nodes on the subnet
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Number 127 126
1)
2
Addresses 0 to 126 0 to 125 -
Remarks Default: 32 addresses
Reserved are:
• address 0 for PG
• address 1 for OP
of those:
1 Master (reserved)
1 PG connection (address 0
reserved)
124 slaves or other masters
-
1)
Note the CPU-specific maximum specifications in the CPU manual.