https://gunkies.org/w/index.php?title=Synchronous_Data_Link_Control&feed=atom&action=historySynchronous Data Link Control - Revision history2024-03-29T00:24:31ZRevision history for this page on the wikiMediaWiki 1.30.0https://gunkies.org/w/index.php?title=Synchronous_Data_Link_Control&diff=26077&oldid=prevJnc: More - a lot more - on top of the framing2022-05-29T07:57:30Z<p>More - a lot more - on top of the framing</p>
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<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>The checksum covers the address, control and data fields. The frame is followed either by i) another frame, or ii) the idle pattern - back-to-back flags (with the trailing '0' bit of one flag overlaid with the starting '0' bit of the next flag).</div></td><td class='diff-marker'> </td><td style="background-color: #f9f9f9; color: #333333; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #e6e6e6; vertical-align: top; white-space: pre-wrap;"><div>The checksum covers the address, control and data fields. The frame is followed either by i) another frame, or ii) the idle pattern - back-to-back flags (with the trailing '0' bit of one flag overlaid with the starting '0' bit of the next flag).</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color:black; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">On top of that, there is an entire other complex layer of protocol, using various values in the 'Control' field: initialization, testing, station identification, configuration, etc. (See the SDLC documentation for more.)</ins></div></td></tr>
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</table>Jnchttps://gunkies.org/w/index.php?title=Synchronous_Data_Link_Control&diff=26072&oldid=prevJnc: Jnc moved page SDLC to Synchronous Data Link Control: Full name2022-05-28T17:19:26Z<p>Jnc moved page <a href="/wiki/SDLC" class="mw-redirect" title="SDLC">SDLC</a> to <a href="/wiki/Synchronous_Data_Link_Control" title="Synchronous Data Link Control">Synchronous Data Link Control</a>: Full name</p>
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<td colspan="1" style="background-color: white; color:black; text-align: center;">Revision as of 17:19, 28 May 2022</td>
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</td></tr></table>Jnchttps://gunkies.org/w/index.php?title=Synchronous_Data_Link_Control&diff=26071&oldid=prevJnc: Covers the basics2022-05-28T17:18:50Z<p>Covers the basics</p>
<p><b>New page</b></p><div>'''Synchronous Data Link Control''' (usually abbreviated to '''SDLC''') is a [[protocol]] used to transmit [[packet]]s over [[synchronous serial line]]s. It can operate over both [[half-duplex]] and [[full-duplex]] links; supported configurations include both point-point and [[multi-point]]. The later protocol [[High-Level Data Link Control|HDLC]] is based on SDLC.<br />
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SDLC sends 8-bit bytes only. The start and end of the packet (named a 'frame' in SDLC terminology) are marked by a specific bit pattern, '01111110', the 'flag'. Instances of that pattern in the user data are obscured by [[bit stuffing]] - '11111' is replaced, during transmission, by '111110'; the inserted '0' is removed on reception. <br />
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If the link does not provide an independent received [[clock]], SDLC uses [[Non Return to Zero Inverted|NRZI]] encoding, to ensure that enough transitions are present to keep the clock synchronized. With NRZI, the bit stuffing used when the data contains long runs of '1' bits provides enough transitions.<br />
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An SDLC frame contains these fields:<br />
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* Flag - 8 bits<br />
* Address - 8 bits<br />
* Control - 8 bits<br />
* Data - Variable number of 8-bit bytes<br />
* [[Checksum]] - 16 bits<br />
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The checksum covers the address, control and data fields. The frame is followed either by i) another frame, or ii) the idle pattern - back-to-back flags (with the trailing '0' bit of one flag overlaid with the starting '0' bit of the next flag).<br />
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{{semi-stub}}<br />
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==External links==<br />
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* [http://www.bitsavers.org/pdf/ibm/datacomm/GA27-3093-2_SDLC_General_Information_Mar79.pdf IBM Synchronous Data Link Control: General Information]<br />
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[[Category: Serial Lines]]</div>Jnc