The third level of Ethernet addressing is the UDP or TCP port number. The Galil board does not require a specific
port number. The port number is established by the client or master each time it connects to the DMC-40x0 board.
Typical port numbers for applications are:
Port 23: Telnet
Port 502: Modbus
Communicating with Multiple Devices
The DMC-40x0 is capable of supporting multiple masters and slaves. The masters may be multiple PC's that send
commands to the controller. The slaves are typically peripheral I/O devices that receive commands from the
controller.
NOTE: The term "Master" is equivalent to the internet "client". The term "Slave" is equivalent to the internet
"server".
An Ethernet handle is a communication resource within a device. The DMC-40x0 can have a maximum of 8
Ethernet handles open at any time. When using TCP/IP, each master or slave uses an individual Ethernet handle. In
UDP/IP, one handle may be used for all the masters, but each slave uses one. (Pings and ARPs do not occupy
handles.) If all 8 handles are in use and a 9
th
master tries to connect, it will be sent a "reset packet" that generates the
appropriate error in its windows application.
NOTE: There are a number of ways to reset the controller. Hardware reset (push reset button or power down
controller) and software resets (through Ethernet or RS232 by entering RS). The only reset that will not cause the
controller to disconnect is a software reset via the Ethernet.
When the Galil controller acts as the master, the IH command is used to assign handles and connect to its slaves.
The IP address may be entered as a 4 byte number separated with commas (industry standard uses periods) or as a
signed 32 bit number. A port number may also be specified, but if it is not, it will default to 1000. The protocol
(TCP/IP or UDP/IP) to use must also be designated at this time. Otherwise, the controller will not connect to the
slave. (Ex. IHB=151,25,255,9<179>2 This will open handle #2 and connect to the IP address 151.25.255.9, port
179, using TCP/IP)
Which devices receive what information from the controller depends on a number of things. If a device queries the
controller, it will receive the response unless it explicitly tells the controller to send it to another device. If the
command that generates a response is part of a downloaded program, the response will route to whichever port is
specified as the default (unless explicitly told to go to another port with the CF command). To designate a specific
destination for the information, add {Eh} to the end of the command. (Ex. MG{EC}"Hello" will send the message
"Hello" to handle #3. TP,,?{EF} will send the z axis position to handle #6.)
Multicasting
A multicast may only be used in UDP/IP and is similar to a broadcast (where everyone on the network gets the
information) but specific to a group. In other words, all devices within a specified group will receive the
information that is sent in a multicast. There can be many multicast groups on a network and are differentiated by
their multicast IP address. To communicate with all the devices in a specific multicast group, the information can be
sent to the multicast IP address rather than to each individual device IP address. All Galil controllers belong to a
default multicast address of 239.255.19.56. The controller's multicast IP address can be changed by using the IA> u
command.
Using Third Party Software
Galil supports DHCP, ARP, BOOT-P, and Ping which are utilities for establishing Ethernet connections. DHCP is a
protocol used by networked devices (clients) to obtain the parameters necessary for operation in an Internet Protocol
network. ARP is an application that determines the Ethernet (hardware) address of a device at a specific IP address.
BOOT-P is an application that determines which devices on the network do not have an IP address and assigns the
IP address you have chosen to it. Ping is used to check the communication between the device at a specific IP
address and the host computer.
DMC-40x0 User Manual Chapter 4 Software Tools and Communication • 52
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