Task Code Port - Hitachi HIDIC EH-150 Applications Manual

6.2

Task code port

EH-ETH has four logical ports for task code communication.
Task code port supports TCP and UDP of data link layer. Table 6.2 shows the comparison to use.
Open request/ close request procedure
Communication with LADDER Editor for
Windows®
Reliability of the data in a data link layer level
[For host computer programmer]
- When you select TCP
1.Because all task ports are "LISTEN" (passive), you need to open connection before sending task code.
- When you select UDP,
1. UDP protocol does not have high reliability of communication, application program needs to confirm the
response, and control re-sending and packet order.
2. You do not have to open connection before issuing task code.
Caution
- Task code port can not transmit data actively regardless of TCP or UDP protocol.
- Task Code ports may stop responding, when a EH-ETH got a problem in network. Please set up a timeout
value for Task Code ports, in order for you to avoid this problem.
Importance
[Retry action of Open request for active port]
When an other station to a response cannot be found to the open request that EH-ETH sends, EH-ETH sends
the TCP packet which contains the "SYN" flag at intervals of the following time.
ARP packet sends->6s->12s->24s->48s->64s->64s->64s->64s->64s->64s->64s->64s
In other words, EH-ETH stops the retry action of open request after about 10 minutes, after sending an ARP
packet.
(1). When "less than 10 minutes" is set as an ASR connection timeout value.
- When EH-ETH detects a timeout, ERR LED is turned on red.
- After a timeout is detected, the retry action of Open request is done continuously.
(2). When "10 minutes or more" is set as an ASR connection timeout value.
- When all the retry action of Open request is completed, ERR Light Emitting Diode lights up red.
Table 6.2
Compression Item
Chapter 6 Task code communication
Task code port
TCP
Host side: Need
EH-ETH side: No
Possible
High
6-4
UDP
Host side: No
EH-ETH side: No
Not possible
Low