User guide

Quantum Ethernet TCP/IP Modbus Application Protocol
82
840 USE 115 00 Version 1.0
C.3 TCP/IP Specific Issues
C.3.1 Broadcast/Multicast
Althou
g
h broadcast and/or multicast are supported b
y
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
y
er.
Schneider Automation’s Quantum PLCs use broadcast addressin
g
because the
y
use ARP as the means of locatin
g
the destination node. The client interface to the
Modbus Application Protocol service on the PLC, the MSTR block, re
q
uires the
user to provide the destination IP address. Also the embedded stack does use a
pre-confi
g
ured default
g
atewa
y
IP address in the case where ARP does not
succeed.
C.3.2 TCP Port Number
Schneider Automation has obtained a well-known s
y
stem port from an Internet
Authorit
y
. Schneider Automation’s well-known s
y
stem port number is 502. The
Internet Authorit
y
assi
g
ned the s
y
stem port number 502 to asa-appl-proto with
Dennis Dubé as the compan
y
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
y
the value of
the proto_id parameter in the mbap_pdu. Currentl
y
the onl
y
assi
g
nment is 0
meanin
g
Modbus Application Protocol.