Specifications

2 - 12
(In TCP/IP communication)
• The connection is established when the open processing is completed
normally.
• When the close processing performed after completion of the data
communication is normally completed, the connection is disconnected.
• There are the following methods for establishing a connection: Active
open and Passive open.
(Active open)
Active open makes a request to establish a connection to the
designated external device that is waiting for connection
establishment.
Compared to the telephone line, it is a caller side.
(Passive open)
There are Fullpassive open and Unpassive open.
Compared to the telephone line, it is a receiver side.
The open and close processing by Passive open on the Ethernet
module side can be performed from PLC CPU or the Ethernet module
system. (*1)
(Fullpassive open)
Fullpassive open waits for a connection establishment request (Active
open) addressed to the local station from the designated external
device.
(Unpassive open)
Unpassive open waits for a connection establishment request (Active
open) addressed to the local station from any external devices.
(Diagram of connection establishing procedure)
PLC CPU
PLC CPU
Initial processing
Initial processing
Initial completion
Initial completion
Initial completion
Fullpassive/
Unpassive
open
Open completion
Open completion
Ethernet module
Initial request
Open
Waiting for
open request
Active open
Open request
Open completion
Open completion
Initial completion
Ethernet module
Initial request
(In UDP/IP communication)
• The open and close processing is done as internal processing of the
Ethernet module to enable data communication with external devices.
• A connection is established during data communication after the open
processing is completed normally.
• The open and close processing on the Ethernet module side in the
UDP/IP communication can be performed from the PLC CPU or the
Ethernet module system. (*1)