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Daisy chain (electrical engineering)
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<h2 id="signal-transmission">Signal transmission</h2> <p class="note">See also: <a href="/facts/Passthrough_(electronics)/h3VLN8vr">Passthrough (electronics)</a></p> <p>For <a href="/facts/Analog_signal/xDbb4uB5">analog signals</a>, connections usually consist of a simple <a href="/facts/Bus_(computing)/R45TKwS7">electrical bus</a> and, especially in the case of a <a href="/facts/Signal_chain_(signal_processing_chain)/6C5aPXcL">chain of many devices</a>, may require the use of one or more <a href="/facts/Repeater/JTkWvTEP">repeaters</a> or <a href="/facts/Amplifier/pnRgxncC">amplifiers</a> within the chain to counteract <a href="/facts/Attenuation/XP4vX360">attenuation</a> (the natural loss of energy in such a system). <a href="/facts/Digital_signal_(electronics)/pKYKbxfK">Digital signals</a> between devices may also travel on a simple electrical bus, in which case a bus <a href="/facts/Electrical_termination/MatLrePo">terminator</a> may be needed on the last device in the chain. However, unlike analog signals, because digital signals are <a href="/facts/Discrete_signal/RR8wpS9e">discrete</a>, they may also be electrically regenerated, but not modified, by any device in the <a href="/facts/Signal_chain_(signal_processing_chain)/6C5aPXcL">chain</a>. </p> <h2 id="types">Types</h2> <h3>Computer hardware</h3> <p>Some hardware can be attached to a computing system in a daisy chain configuration by connecting each component to another similar component, rather than directly to the computing system that uses the component. Only the last component in the chain directly connects to the computing system. For example, chaining multiple components that each have a <a href="/facts/Universal_asynchronous_receiver/transmitter/xMntJcsI">UART</a> port to each other. The components must also behave cooperatively. e.g., only one seizes the communications bus at a time. </p> <ul><li><a href="/facts/SCSI/pxXulrBr">SCSI</a> is an example of a digital system that is electrically a <a href="/facts/Computer_bus/R45TKwS7">bus</a>, in the case of external devices, is physically wired as a daisy chain. Since the network is electrically a bus, it must be terminated and this may be done either by plugging a terminator into the last device or selecting an option to make the device terminate internally.</li> <li><a href="/facts/MIDI/tblhmeFV">MIDI</a> devices are usually designed to be wired in a daisy chain. It is normal for a device to have both a THRU port and an OUT port and often both can be used for chaining. The THRU port transmits the information through with minimal delay and no alteration, while the OUT port sends a completely regenerated signal and may add, remove, or change messages, at the cost of some delay in doing so. The difference can result in the signals arriving at different times; if the chain is long enough, it will be distorted so much that the system can become unreliable or non-functional.</li> <li>Some <a href="/facts/Serial_Peripheral_Interface_Bus/uSCU56eG">Serial Peripheral Interface Bus</a> (SPI) IC products are designed with daisy chain capability.</li> <li>All <a href="/facts/JTAG/IxRc5rG7">JTAG</a> integrated circuits should support daisy chaining according to JTAG daisy chaining guidelines.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a></li> <li><a href="/facts/Thunderbolt_(interface)/x6pqMKHY">Thunderbolt (interface)</a> also supports daisy-chained devices such as <a href="/facts/RAID/IpzWWgog">RAID</a> arrays and <a href="/facts/Computer_monitors/NRaTDFHc">computer monitors</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a></li> <li><a href="/facts/DisplayPort/rJSvGhBN">DisplayPort</a> 1.2 and higher features Multi-Stream Transport (MST) mode. In this mode, multiple screens can be connected either using a hub or as a daisy chain.</li> <li>The <a href="/facts/Hexbus/R6tIhNEn">Hexbus</a> is the 10-wire bus of <a href="/facts/Texas_Instruments/88NUhuHF">Texas Instruments</a>, used in the <a href="/facts/TI-99/4A/9YWyzBhp">TI-99/4A</a>, <a href="/facts/CC-40/QwEuzDC5">CC-40</a> and <a href="/facts/TI-74/pC5JkaHy">TI-74</a>.</li></ul> <h3>Network topology</h3> <p class="note">Main article: <a href="/facts/Network_topology/rBYE0kke">Network topology § Daisy chain</a></p> <p>Any particular daisy chain forms one of two network topologies: </p> <ul><li>Linear topology: For example, A-B-C-D-E, A-B-C-D-E & C-M-N-O (branched at C) are daisy chain.</li> <li>Ring topology: there is a loop connection back from the last device to the first. For example, A-B-C-D-E-A (loop). This is often called a "daisy chain loop".<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a></li></ul> <h3>System access</h3> <p class="note">See also: <a href="/facts/Jump_server/dhEA5U3G">Jump server</a></p> <p>Users can daisy chain computing sessions together. Using services such as <a href="/facts/Telnet/hxT0e85h">Telnet</a> or <a href="/facts/Secure_Shell/wjVRw5zv">SSH</a>, the user creates a session on a second computer via Telnet, and from the second session, Telnets to a third and so on. Another typical example is the "terminal session inside a terminal session" using <a href="/facts/Remote_Desktop_Protocol/A5e9ILdI">Remote Desktop Protocol</a>. Reasons to create daisy chains include connecting to a system on a non-routed network via a gateway system, preserving sessions on the initial computer while working on a second computer, to save bandwidth or improve connectivity on an unstable network by first connecting to a better connected machine. Another reason for creating a daisy chain is to camouflage activity while engaged in <a href="/facts/Cybercrime/cSyaFF96">cybercrime</a>. </p> Look up <i>daisy chain</i> in Wiktionary, the free dictionary. <h2 id="references">References</h2> <ol> <li id="fn:1"><p>maxim-ic.com - Electrical Engineering Glossary Definition for Daisy Chain <a href="http://www.maxim-ic.com/glossary/index.cfm/Ac/V/ID/71/Tm/Daisy_Chain" target="_blank">http://www.maxim-ic.com/glossary/index.cfm/Ac/V/ID/71/Tm/Daisy_Chain</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"ViaTAP user's manual, chapter Design guidelines for use with ViaTAP" (PDF). Archived from the original (PDF) on 2017-02-22. Retrieved 2009-01-08. <a href="https://web.archive.org/web/20170222084446/http://jtagtest.com/downloads/viatap.pdf" target="_blank">https://web.archive.org/web/20170222084446/http://jtagtest.com/downloads/viatap.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Thunderbolt™ for Developers". Intel. Retrieved 2020-04-02. <a href="https://www.intel.com/content/www/us/en/products/docs/io/thunderbolt/thunderbolt-technology-developer.html" target="_blank">https://www.intel.com/content/www/us/en/products/docs/io/thunderbolt/thunderbolt-technology-developer.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>IR3508Z data sheet (PDF), archived from the original (PDF) on 2016-03-03, The last phase IC is connected back to ... the control IC to complete the daisy chain loop <a href="https://web.archive.org/web/20160303230442/http://www.irf.com/product-info/datasheets/data/ir3508zmpbf.pdf" target="_blank">https://web.archive.org/web/20160303230442/http://www.irf.com/product-info/datasheets/data/ir3508zmpbf.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Joel Konicek; Karen Little (1997). Security, ID Systems and Locks: The Book on Electronic Access Control. p. 170: daisy chain loop illustration. <a href="https://books.google.com/books?id=9ffCiw9fUncC&dq=%22daisy+chain+loop%22&pg=PA170" target="_blank">https://books.google.com/books?id=9ffCiw9fUncC&dq=%22daisy+chain+loop%22&pg=PA170</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> </ol>