pdf - Opto 22 SNAP Ethernet I/O Frequently Asked Questions (FAQ)
pdf - Opto 22 SNAP Ethernet I/O Frequently Asked Questions (FAQ)
pdf - Opto 22 SNAP Ethernet I/O Frequently Asked Questions (FAQ)
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<strong>Opto</strong> <strong>22</strong> <strong>SNAP</strong> <strong>Ethernet</strong> I/O: <strong>Frequently</strong> <strong>Asked</strong> <strong>Questions</strong> (<strong>FAQ</strong>) pg. 3/12<br />
1.00 About <strong>Ethernet</strong> (cont.)<br />
1.20 How do the <strong>Ethernet</strong>, TCP/IP, and application layer protocols fit together?<br />
The following table outlines how the pieces of an <strong>Ethernet</strong> and TCP/IP communications<br />
system works:<br />
E-mail, paging<br />
SMTP<br />
<strong>Opto</strong> <strong>22</strong> supported protocols<br />
<strong>Opto</strong> <strong>22</strong>’s IEEE<br />
1394-based<br />
protocol<br />
Transport Control Protocol (TCP)<br />
Internet Protocol (IP)<br />
Modbus/TCP<br />
protocol<br />
SNMP,<br />
streaming area<br />
Physical interface<br />
For example, an <strong>Ethernet</strong> card and cable or modem (coaxial, twisted pair, fiber<br />
optic, dial-up, wireless)<br />
1.21 That seems very confusing. Is there an easier way of looking at it?<br />
Internet<br />
Model<br />
Application<br />
UDP Transport<br />
Internet<br />
Physical<br />
Actually, there is. You can break the technology down into three major parts, from top<br />
to bottom:<br />
• Application layer—This is where the application level protocol resides. Examples<br />
of application level protocols include Modbus/TCP and Simple Mail Transport Protocol (SMTP).<br />
Several application protocols are supported with the <strong>SNAP</strong> <strong>Ethernet</strong> brain, and all can be used<br />
simultaneously. For example, since both Modbus/TCP and SMTP are supported on the <strong>SNAP</strong><br />
<strong>Ethernet</strong> brain, you could retrieve data from the <strong>Ethernet</strong> brain using a product like<br />
Wonderware’s Intouch, while the brain simultaneously sends e-mail to alert a technician about a<br />
problem. <strong>Opto</strong> <strong>22</strong>’s own IEEE 1394-based memory map protocol is also supported<br />
at the application layer.<br />
• Transport layer—The transport layer encompasses the TCP/IP protocol suite,<br />
and is arguably the most important. All messages transferred between a host and the <strong>SNAP</strong><br />
<strong>Ethernet</strong> brain are encapsulated in a TCP or User Datagram Protocol (UDP) packet. Therefore,<br />
any application layer protocol that works with a socket interface (and therefore TCP/IP) can be<br />
used with this transport layer without regard to the physical layer. Furthermore, any physical<br />
layer component that works with TCP/IP can be used (again, without regard to the top<br />
application layer).<br />
• Physical layer—The physical layer includes only the actual physical connection to a<br />
device, such as <strong>Ethernet</strong>, fiber-optic, or serial. The <strong>SNAP</strong> <strong>Ethernet</strong> brain currently supports<br />
<strong>Ethernet</strong> Category 5 or superior twisted-pair cabling and has an RS-232 serial port for use with<br />
modems. The <strong>SNAP</strong>-WLAN-FH-ADS brain offers a wireless LAN option. Fiber-optic support is<br />
available through an external fiber-to-copper transceiver.<br />
<strong>Opto</strong> <strong>22</strong> 43044 Business Park Drive Temecula, CA 92590 Phone: (909)695-3000 (800)321-OPTO Fax: (909)695-3095 Internet : www.opto<strong>22</strong>.com<br />
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