Presetting - Hitachi EH-150 Applications Manual

7.2

Presetting

Before the data communication, you have to establish connection against to the other port. Here after, an
enabled connection is called as "opened connection", and a disabled connection is called as "closed
connection".
Caution
EH-ETH2 has 10 connections. 4 connections are only for task code communication, 6 connections are ASR
connections for message communication.
For reference
To open or close TCP/IP connection is like telephone call in our daily life.
For instance, a telephone of A is assumed as EH-ETH2, telephone of B as a host computer.
In case A calls B, when B is ready to receive, B can pick up the receiver. Now both A and B are ready to
speak. On the other hand, when B is not ready to pick up the receiver, A must hang up the receiver and
give up conversation.
This is replaced to TCP/IP communication. In order EH-ETH2 (A) to communicate with the host computer
(B), EH-ETH2 (A), which is specified as active node, must request to open the connection with specifying
the destination (IP address and port number of B).
If the host computer (B) is ready to receive the request, the communication is opened and ready to be
talked.
On the other hand, when the host computer (B) is not ready to open the connection, EH-ETH2 (A) must
give up the request after connection time out. In this case, EH-ETH2 (A) can not communicate with host
computer.
In addition, such receiving (passive) station (B in this case) can get any requests from other than A, and
can answer (open) to all the requests. If B should open connection upon all the request, the setting
"Other station" must be "Optional". But if B should open connection upon the request from A only, this
must be "Specified", and the IP address and port number must be specified as well.
In short, a station specified as active must specify the destination. On the other hand, a station specified
as passive can be selected "specified other station" or "optional other station".
: Other station "Specified" and "Optional"
Chapter 7 Automatic Sending/Receiving function (ASR)
7-4