Communicating With Multiple Devices - Galil Motion Control DMC-14 5 Series Manual

NOTE: Galil strongly recommends that the IP address selected is not one that can be accessed across
the Gateway. The Gateway is an application that controls communication between an internal network
and the outside world.
The third level of Ethernet addressing is the UDP or TCP port number. The Galil controller does not
require a specific port number. The port number is established by the client or master each time it
connects to the controller.

Communicating with Multiple Devices

The DMC-14XX 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-14XX can have a
maximum of 6 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 6 handles are in use and a 7
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)
An additional protocol layer is available for speaking to I/O devices. Modbus is an RS-485 protocol
that packages information in binary packets that are sent as part of a TCP/IP packet. In this protocol,
each slave has a 1 byte slave address. The DMC-14XX can use a specific slave address or default to
the handle number.
The Modbus protocol has a set of commands called function codes. The DMC-14XX supports the 10
major function codes:
Function Code
01
02
03
04
05
06
07
15
16
17
42 Chapter 4 Communication
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Definition
Read Coil Status (Read Bits)
Read Input Status (Read Bits)
Read Holding Registers (Read Words)
Read Input Registers (Read Words)
Force Single Coil (Write One Bit)
Preset Single Register (Write One Word)
Read Exception Status (Read Error Code)
Force Multiple Coils (Write Multiple Bits)
Preset Multiple Registers (Write Words)
Report Slave ID
th
master tries to
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