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Manual – MOVI-PLC® advanced DHR41B for EtherNet/IP, Modbus/TCP and PROFINET IO
73
8
Connection management
The Modbus Protocol (Modbus/TCP)
Objects
DHR41B
8.3
Connection management
Up to 8 simultaneous Modbus connections are possible, max. one of which has write
access to the process data area (controlling connection).
Connections that are no longer used must be dropped by the master. If a ninth connec-
tion is to be established and the slave detects a connection that is no longer active, it is
severed on one side by the slave because it assumes that the associated master is no
longer active. If there are 8 active connections, the attempt to establish a ninth connec-
tion is cancelled (socket is closed on the server). Connections 1 - 8 operate indepen-
dently of each other. There is no prioritization. Only one controlling connection that can
change process data is permitted.
If a controlling connection has already been established via EtherNet/IP, you cannot es-
tablish another controlling connection via Modbus/TCP. The slave can at least buffer
one frame with maximum Modbus length on receipt or transmission.
8.3.1
Sending process output data (requesting a controlling connection)
Sending process output data is only permitted if the connection already is a controlling
connection or if there is no controlling connection. If the unit accepts the connection, it
transfers the process output data to the process data image or transmits the process
data to a lower-level station (gateway operation). As long as this connection is activated,
no other master can change the process output data (PO data).
Object ID Name
Type
M/O
Category
Value (example)
0x00
VendorName
ASCII
String
Mandatory
Basic
"SEW-EURODRIVE"
0x01
ProductCode
"SEW MOVI-PLC ADVANCED
DHR41B"
0x02
MajorMinorRevisions
"823 568 0.10" (example)
0x03
VendorUrl
Optional
Regular
"www.sew.de"
0x04
ProductName
"SEW MOVI-PLC ADVANCED"
0x05
ModelName
"DHR41B"
0
0
I
Содержание DHR41B
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