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App - 19
MELSEC-F
APPENDIX
App - 19
Appendix 5 Differences between the Ethernet and the IEEE802.3
The following shows the Ethernet header in the data link layer supported by the
Ethernet module.
(1) Ethernet
(2) IEEE802.3
Appendix 6 ICMP Protocol Supported by the Ethernet Module
The following table outlines the types of ICMP supported by the Ethernet module and
the processing performed by the Ethernet module.
*1 The Ethernet module can simultaneously receive two ICMP ECHO requests (type 8, Ping message), which are used for
existence confirmation, etc., and handles them accordingly.
When three or more ICMP ECHO requests are received at the same time, the third and succeeding requests will be
ignored.
If a response is not returned to the external device when an ICMP ECHO request is sent to the Ethernet module, send
an ICMP ECHO request to the Ethernet module again.
The Ethernet module is able to receive a maximum of 1460 bytes ICMP message at one time.
Do not send an ICMP message request exceeding 1460 bytes to the Ethernet module.
Ethernet data link layer header Ethernet module
Ethernet frame (V 2.0) specification
IEEE802.3 (ISO/IEC8802.3) frame specification
ICMP Type ICMP name/description Processing by the Ethernet module
0
Echo Reply
Result of IP packet loopback
Upon receiving an Echo Request, the Ethernet module
sends this message.
8
Echo Request
Requests loopback of IP packet
If destination existence confirmation is set in the buffer
memory, the Ethernet module sends this message when
attempting to confirm the existence of the target. (*
1
)
Others — Ignored by the Ethernet module. (Not supported)
Destination address Source address Type Data (46 to 1500 bytes) FCS
Destination address Source address Length Data (46 to 1500 bytes) FCS