
Quantum Ethernet TCP/IP Modbus Application Protocol
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840 USE 115 00 Version 1.0
C.3 TCP/IP Specific Issues
C.3.1 Broadcast/Multicast
Althou
h broadcast and/or multicast are supported b
both IP network address and
IEEE 802.3 MAC address, the Modbus Application Protocol does not support either
broadcast or multicast at the application la
er.
Schneider Automation’s Quantum PLCs use broadcast addressin
because the
use ARP as the means of locatin
the destination node. The client interface to the
Modbus Application Protocol service on the PLC, the MSTR block, re
uires the
user to provide the destination IP address. Also the embedded stack does use a
pre-confi
ured default
atewa
IP address in the case where ARP does not
succeed.
C.3.2 TCP Port Number
Schneider Automation has obtained a well-known s
stem port from an Internet
Authorit
. Schneider Automation’s well-known s
stem port number is 502. The
Internet Authorit
assi
ned the s
stem port number 502 to asa-appl-proto with
Dennis Dubé as the compan
point of contact.
This port number allows Schneider Automation to transport various application
protocols over with TCP or UDP. The particular protocol is indicated b
the value of
the proto_id parameter in the mbap_pdu. Currentl
the onl
assi
nment is 0
meanin
Modbus Application Protocol.
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