Modbus Rtu; General; Communications - Eaton PowerXL DA1 Communications Manual

2 Modbus RTU

2.1 General

2.2 Communications

HMI-PLC
Modbus is a centrally polled bus system in which a so-called master (PLC)
controls the entire data transfer on the bus. Internode communication
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).
￫
More information on Modbus can be found under
www.modbus.org
L1/ L L2/ N
RS485
Modbus RTU
0 V +10 V 1
2
3 4
U
V
RJ45
Figure 2: Modbus line with variable frequency drives/variable speed starters
a Splitter DX-SPL-RJ45... (T-plug connector)
b DX-CBL-RJ45... connection cable
c DX-SPL-RJ45... splitter with bus termination resistor
Modbus RTU for variable frequency drive DA1, DC1, DE1 09/16 MN040018EN www.eaton.com
.
DE1
L3

13 14
W

①
②
DC1

L1 /L L2 /N
L3
CO M
1
2 3
4
5 6
7
8 9 10 11

U
V
W
①
②
2 Modbus RTU
2.1 General
DA1

DC -
L1 /L L2 /N
L3

DC + BR
U
V
W
③
9