Eaton DC1-124D1FN-A20N - Serial interface (Modbus RTU)

7 Serial interface (Modbus RTU)
7.1 General
DC1 Frequency Inverter 10/12 MN04020003Z-EN www.eaton.com 141
7 Serial interface (Modbus RTU)
7.1 General
Modbus is a centrally polled bus system in which a so-called master (PLC)
controls the entire data transfer on the bus. Cross-traffic between the
individual modules (slaves) is not possible.
Every single data transfer operation is initiated by the master with a request.
Only one request can be sent on the cable at a time.
Slaves are not able to initiate transfers, and are only able to respond to
requests.
Two types of dialog are possible between master and slave:
• The master sends a request to a slave and waits for a response.
• The master sends a request to all slaves and does not wait for a
response (broadcast).
7.1.1 Communication
Figure 82: Modbus network with DC1
The figure shows a typical setup with a host computer (master) and any
number (a maximum of 63 modules) of DC1 frequency inverters (slaves) .
Each frequency inverter has a unique address on the network.
Addresses are
assigned individually
to each DC1 frequency inverter with the P-36 parameter
and are independent of their physical connection (position) within the net-
work.
￫
More information on Modbus can be found under
www.modbus.org.
Host computer
L1/L
L2/N
L3
U
V
W
1
2
3
4
5
6
7
8
9
10
11
1
①②
Host computer
L1/L
L2/N
L3
U
V
W
1
2
3
4
5
6
7
8
9
10
11
L1/L
L2/N
L3
U
V
W
1
2
3
4
5
6
7
8
9
10
11
L1/L
L2/N
L3
U
V
W
1
2
3
4
5
6
7
8
9
10
11
2 3 63