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User Manual For Cyclone LC Programmers 112 10.3 Internet Protocol Once the network has been established, and the IP numbers have been assigned, data can be transacted over a network with one of several protocols. By far …
User Manual For Cyclone LC Programmers 111
10 ETHERNET CONFIGURATION
This section describes the mechanism used by the Cyclone device to transact data over an
Ethernet network. It primarily focuses on the User Datagram Protocol (UDP), which is a popular
method for sending data over a network when the speed of a data transaction is of more concern
than the guarantee of its delivery. The Cyclone takes advantage of the UDP protocol’s penchant
for speed, and adds an extra layer of logic to guarantee the delivery of UDP packets in order to
offer a best-of-both-worlds solution.
10.1 Network Architectures
Before delving into the innards of Ethernet message passing, it is prudent to briefly describe the
different network architectures in use today, and how they pertain to the operation of the Cyclone.
Computers are, of course, connected to one another through intermediary devices in order to form
networks. There are several classes of these intermediary devices, but they generally fall into one
of the following three groups:
Hubs
At the most basic level, computers are connected to one another through a Hub. A Hub is
a device with several ports that are used to connect multiple computers together. It is a
repeater device – a Hub simply copies the data incoming on one port as data outgoing on
the other ports. In this manner, if there are four computers connected through a Hub, and if
the first computer is sending data to the second computer, then the third and the fourth
computers will also receive an identical copy of that data. Hubs are usually used to set up
a small Local Area Network (LAN), which may have on the order of 10 to 20 computers.
Switches
The aforementioned type of process, where the data is simply replicated onto every
available port, quickly becomes inefficient for larger sized networks. For this reason, a
larger sized LAN employs the usage of Switches instead of Hubs. A Switch is essentially a
smart Hub, in that it limits the input and output of data to the two transacting computers.
Routers
Larger networks, such as Wide Area Networks (WANs), or the Internet for that matter, use
progressively more sophisticated devices to transact data. At the core of these devices is
the Router, which functions as a switch between networks.
The Cyclone performs irrespective of the connection mechanism, with one very important caveat:
it needs to be set up with the appropriate network parameters for the underlying network
architecture.
10.2 Network Parameters
A typical network becomes operational not after the physical connections have been established,
but after network parameters in the form of IP (Internet Protocol) numbers have been assigned to
the individual computers. An IP number is a unique string that consists of four numbers ranging
between 0 and 255, separated by dots, e.g., 192.168.1.2. Every computer that is on a network
needs to have a unique IP number. The computer uses this IP number to identify itself on the
network, and also to address the recipient of its data.
Assignation of this IP number is sufficient information to transact data on a simple network
connected by a hub. On a more complex network, however, routing information becomes
important. The routing information consists of two more IP numbers. The first of these is called the
Subnet Mask, and is used to determine whether or not the destination address resides on the
same subnet (i.e., doesn’t need to be forwarded to another network). The other IP number is the
Gateway Address, which is the address of the computer that handles forwarding and receiving of
packets to and from other networks.
Before first use, the Cyclone needs to be programmed with a unique IP number, the Subnet Mask
IP number, and also the default Gateway’s IP number. This can be done via the USB or the Serial
port, and is described in greater detail in the “Configuring the Cyclone” section of this manual.
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10.3 Internet Protocol
Once the network has been established, and the IP numbers have been assigned, data can be
transacted over a network with one of several protocols. By far the most prevalent protocol is the
Transmission Control Protocol (TCP), which runs on top of the Internet Protocol in what is
collectively known as the TCP/IP protocol. The TCP/IP protocol was developed by the Department
of Defense to connect different computers from different vendors by a “network of networks,” which
has become what is known as the Internet today.
The primary purpose of the TCP/IP protocol was to prevent a complete network outage in the case
of a nuclear attack, by automatically rerouting data traffic through the functioning part of the
network. As such, the TCP/IP mechanism guaranteed delivery of data packets by introducing a
system of acknowledgments and sequence numbers for the data packets. This mechanism, while
good for transacting large amounts of data (such as email or file transfers), is unsuitable in the
real-time type environment in which the Cyclone operates. Because the Cyclone needs to transact
data as quickly as possible to the target, it takes advantage of TCP/IP’s alternative, the UDP/IP
protocol.
Unlike TCP/IP, the UDP/IP protocol is a connectionless, single-packet protocol that sends short
data packets at the expense of not guaranteeing their delivery. This makes the UDP/IP protocol
efficient in real-time applications such as broadcasting video over the Internet, where the
occasional loss of a frame of data is not going to hamper the overall viewing experience. Left
unmodified, the UDP/IP, with its lack of guarantees for packet delivery, would be unusable in an
environment where the delivery of a single byte of data needs to be guaranteed. The Cyclone
firmware adds mechanisms to the UDP/IP protocol, without affecting its underlying efficiency, to
guarantee delivery of data packets.
10.4 Connecting The Cyclone Device
There are two methods for establishing a connection between a Cyclone and a PC with an
Ethernet cable. The most basic method is to connect the Cyclone directly to a PC, via a cross-over
Ethernet cable. However, the more common method is to place the Cyclone and the PC on the
same network through a Hub.
10.4.1 Connecting the Cyclone to the PC over a network
The Cyclone was intended for use on a network of multiple computers (and other Cyclones). There
are many possible network configurations, and to describe them all is beyond the scope of this
document. However, most configurations are a modification of a basic theme, which is that of
connecting one or more PCs through a Hub to one or more Cyclones.
In order to connect these devices to the Hub, you will need to use the provided straight-through
Ethernet cable. The straight-through cable, which is the “standard” Ethernet cable, is used to
connect devices of different types together, such as a PC to a Hub, or a Hub to a Cyclone.
At this point it once again becomes necessary to program the Cyclone with valid IP numbers, the
process for which is described in greater detail in the following section. However, it is important for
the Cyclone and the PCs to have matching Subnet and Gateway IP numbers, and for each to have
a unique IP number on the network. An example of a setting for above is as follows:
IP Number Gateway IP Subnet Mask
PC1 192.168.100.1 192.168.100.3 255.255.255.0
PC2 192.168.100.2 192.168.100.3 255.255.255.0
CYCLONE 192.168.100.4 192.168.100.3 255.255.255.0
Gateway 192.168.100.3 192.168.100.3 255.255.255.0
It is important to briefly touch upon the underlying network architecture, which can be a 10Mb
(Megabit), 100Mb, 10/100Mb, half-duplex, or a full-duplex connection. The details of the underlying
network architecture are beyond the scope of this document, but it is sufficient to note that most
modern network cards, as well as the Cyclone device, have the capability to configure themselves
for the underlying network through the Auto-negotiation mechanism. Auto-negotiation is performed
as soon as a network cable is connected to the device, and it sets the operating parameters of the
User Manual For Cyclone LC Programmers 113
device to match those of the network.
10.4.2 Connecting Cyclone-to-PC via an Ethernet cable
In order to connect the Cyclone to a PC directly via an Ethernet cable, you need to use what is
known as a cross-over cable. A cross-over cable, which is not provided by PEmicro, is normally
used to connect two similar devices such as a PC to a PC, or a Hub to a Hub. It is a cable that has
its receive and transmit wires crossed over so that the similar devices can effectively communicate
with one another.
With this configuration, it is still important to assign IP numbers to both the PC and the Cyclone
device. Although at first glance it may not seem necessary to assign a Gateway address in this
configuration, the Cyclone was designed to operate on a network of more than two computers, and
therefore it needs to be programmed with a Gateway address.
Assuming the desktop’s IP number to be 192.168.100.1, this is an example of the three IP
numbers that would need to be programmed into the Cyclone:
IP Number Gateway IP Subnet Mask
PC 192.168.100.1 none 255.255.255.0
CYCLONE 192.168.100.2 192.168.100.1 255.255.255.0
For more information on programming these IP numbers into the Cyclone device, please see the
following section.
10.5 Cyclone IP Setup Via LCD Menu
When the user is connecting the Cyclone via Ethernet, before the connection is established
between the Cyclone and the network the menu’s Home Screen will display the Cyclone’s IP
address as 0.0.0.0.
Once a connection has been established, the menu’s Home Screen displays the Cyclone’s IP
address and connection setting (Static or Dynamic).
The Ethernet cable can either be attached at the start of Cyclone startup or connected after setup
is complete. The connection with the network will be established when the cable is connected. If
the Ethernet cable is disconnected after setup is complete, the user should be able to simply
reconnect the cable to reestablish networking. However, depending on the setup of the DHCP
server, if the Ethernet cable is left unplugged for a considerable time the IP address may expire
and connection will have to be set up once again. This can be accomplished by restarting the
Cyclone.
10.5.1 Configure Network Settings
To configure network settings for the Cyclone, navigate to the following Menu location:
Main Menu / Configure Cyclone Settings / Configure Network Settings
The following options will be available under Configure Network Settings:
• Show Current IP Settings
• Edit Static IP Settings
• Enable/Disable Dynamic IP
• Edit Cyclone Name
10.5.1.1 Show Current IP Settings
Show Current IP Settings displays the current IP settings, including:
• Current IP Mode
• IP Number
• Mask
• Gateway