Schneider Electric 840 USE 106 0 manual Scanning, Service, Publish, Subscribe, FTP/TFTP Server

	Ethernet Hot Standby Solution
I/O Scanning	The I/O Scanning provides the repetitive exchange of data with remote TCP/IP
Service	nodes I/O devices. While the PLC is running the Primary NOE sends Modbus Read/
	Write, read or write request to remote I/O devices, and transfer data to and from the
	PLC memory. In the secondary controller, the I/O scanning service is stopped.
	When the Hot Standby swap occurs, the Primary NOE closes all connections with
	I/O devices by sending a TCP/IP reset. The I/O scanning service in this NOE is
	standby.
	After the swap, the new Primary NOE re-establishes the connection with each I/O
	devices. It restarts the repetitive exchange of data with these re-connections.
Global Data
	The Hot Standby NOE is one station within a distribution group. Distribution groups
(Publish/	exchange application variables. Exchanging application variables allows the system
Subscribe)	to coordinate all the stations in the distribution group. Every station publishes local
Service	application variable in a distribution group for all other stations and can subscribe to
	remote application variables independent of the location of the producer.
	The communication port has only one multicast address.
	In this network service, the Hot Standby controllers are viewed like only one station.
	The Primary NOE publishes the Hot Standby application variables and receives the
	subscription variables. The Secondary NOE global data service is in a stopped
	state.
	When the Hot Standby swap occurs, the Primary NOE stops the Global Data
	service. The NOE does not publish the local variable during a swap. And after the
	swap, the new Primary NOE starts to publish application variables and to receive the
	subscription variables.
FTP/TFTP Server
	The File Transfer Protocol/Trivial File Transfer Protocol (FTP/TFTP) server is
	available as soon as the module receives an IP address. Any FTP/TFTP client can
	logon to the module. Access requires the correct user name and password. Hot
	Standby allows only one active FTP/TFTP client session per NOE module.
	When the Hot Standby swap occurs, the Primary and Secondary NOEs close the
	FTP/TFTP connection. If a user sends an FTP/TFTP request during the swap, the
	communication is closed.
	Whenever you re-open communication, you must re-enter a user name and a
	password.

840 USE 106 00 January 2003 175