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Enhanced Small Disk Interface
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<h2 id="connector-pinouts">Connector pinouts</h2> ESDI 34-pin control connector pinout<table><tbody><tr><td>GROUND</td><td>1</td><td>2</td><td>~HD SLCT 3</td></tr><tr><td>GROUND</td><td>3</td><td>4</td><td>~HD SLCT 2</td></tr><tr><td>GROUND</td><td>5</td><td>6</td><td>~WRITE GATE</td></tr><tr><td>GROUND</td><td>7</td><td>8</td><td>~CNFG/STATUS</td></tr><tr><td>GROUND</td><td>9</td><td>10</td><td>~XFER ACK</td></tr><tr><td>GROUND</td><td>11</td><td>12</td><td>~ATTENTION</td></tr><tr><td>GROUND</td><td>13</td><td>14</td><td>~HD SLCT 0</td></tr><tr><td>Key (no pin)</td><td>15</td><td>16</td><td>~SECTOR</td></tr><tr><td>GROUND</td><td>17</td><td>18</td><td>~HD SLCT 1</td></tr><tr><td>GROUND</td><td>19</td><td>20</td><td>~INDEX</td></tr><tr><td>GROUND</td><td>21</td><td>22</td><td>~READY</td></tr><tr><td>GROUND</td><td>23</td><td>24</td><td>~XFER REQ</td></tr><tr><td>GROUND</td><td>25</td><td>26</td><td>~DRV SLCT 0</td></tr><tr><td>GROUND</td><td>27</td><td>28</td><td>~DRV SLCT 1</td></tr><tr><td>GROUND</td><td>29</td><td>30</td><td>Reserved</td></tr><tr><td>GROUND</td><td>31</td><td>32</td><td>~READ GATE</td></tr><tr><td>GROUND</td><td>33</td><td>34</td><td>~CMD DATA</td></tr></tbody></table> ESDI 20-pin data connector pinout<table><tbody><tr><td>~DRV SLCTD</td><td>1</td><td>2</td><td>~SECTOR</td></tr><tr><td>~CMD COMPL</td><td>3</td><td>4</td><td>~ADDR MK EN</td></tr><tr><td>GROUND</td><td>5</td><td>6</td><td>GROUND</td></tr><tr><td>+WRITE CLK</td><td>7</td><td>8</td><td>−WRITE CLK</td></tr><tr><td>GROUND</td><td>9</td><td>10</td><td>+RD/REF CLK</td></tr><tr><td>−RD/REF CLK</td><td>11</td><td>12</td><td>GROUND</td></tr><tr><td>+NRZ WRITE</td><td>13</td><td>14</td><td>−NRZ WRITE</td></tr><tr><td>GROUND</td><td>15</td><td>16</td><td>GROUND</td></tr><tr><td>+NRZ READ</td><td>17</td><td>18</td><td>−NRZ READ</td></tr><tr><td>GROUND</td><td>19</td><td>20</td><td>~INDEX</td></tr></tbody></table> <ul><li><a href="http://www.bitsavers.org/pdf/micropolis/ESDI_spec_X3.170-90.pdf">Micropolis ESDI X3.170-90 Interface Specification</a></li> <li><a href="http://www.bitsavers.org/pdf/cdc/discs/wren/77738076D2_CDC_ESDI_Specification_Nov84.pdf">ESDI Specification, Magnetic Peripherals Inc, 1984</a></li> <li><a href="http://www.mcamafia.de/pdf/ibm_esdi_trm.pdf">IBM ESDI Fixed Disk Drive Adapter/A Technical Reference</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Glass, Brett (February 1989). "Hard Disk Interfaces". BYTE. pp. 293–297. Retrieved 2024-10-08. <a href="https://archive.org/details/eu_BYTE-1989-02_OCR/page/n350/mode/1up?view=theater" target="_blank">https://archive.org/details/eu_BYTE-1989-02_OCR/page/n350/mode/1up?view=theater</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> </ol>