Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
PDP-14
open-in-new
<h2 id="hardware">Hardware</h2> <p>The <a href="/facts/12-bit/6q6tqghX">12-bit</a> PDP-14 could hold a maximum of 4K <a href="/facts/Computer_word/2e5umRaj">words</a> for instructions. The system's configuration included a control unit and a number of external boxes:<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <ul><li>I-boxes (BX14) were for discrete inputs from the controlled system. Up to 256 <i>input</i> sources could be addressed.</li></ul> <ul><li>O-boxes (BY14) could control up to 255 <a href="/facts/Actuator/mF9qVJJR">actuators</a> in the controlled system.</li> <li>A-boxes could be filled with timer modules for controlling time-driven events or retentive storage modules which were not cleared with power loss. A-boxes occupied the output <a href="/facts/Address_space/EscyYKkP">address space</a> along with the O-boxes.</li> <li>S-boxes were essentially the same as the O-boxes, but there was no real output device. This enabled storing intermediate results. S-boxes also used the shared output address space.</li></ul> <p>Hence the combined usable output address space of the <i>O-boxes</i>, <i>A-boxes</i> and <i>S-boxes</i> was 255 or fewer. </p> <h3>Registers</h3> <p>The PDP-14 has seven 12-bit <a href="/facts/Processor_register/32RvbUdz">registers</a>:<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p> <ul><li>IR</li> <li>PC1 & PC2</li> <li>MB</li> <li>SPARE</li> <li>INPUT and OUTPUT.</li></ul> <h3>Instructions</h3> <p>Among the PDP-14 instructions were:<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <ul><li>TRR – to move data between some (but not all) of the registers – TRansfer Register (contents).</li></ul> PC1 and SPARE have increment and decrement capabilities, permitting TRR to modify the value loaded into the register. <ul><li>JMS – JuMp to Subroutine – at the address specified in the following 12-bit word, <a href="/facts/Function_(computer_programming)/9vFJrg0A">saving the return address in PC2</a></li> <li>JMR – JuMp to RETURN from a subroutine, jumps to location saved in PC2.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> In effect, JMR is a TRR in which PC2 is transferred to PC1.</li></ul> <ul><li>SKP – SKiP – is a TRR in which PC1 is incremented by 1.</li></ul> <p>There were also TEST instructions (Test if something is ON or OFF) and SET instructions (SYN – Set "Y" oN, SYF – Set "Y" ofF). </p> <h2 id="software">Software</h2> <p>The original PDP-14 required that programming be done by DEC.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>Subsequently,<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> software development for the PDP-14 was done on another system, the <a href="/facts/PDP-8/udvrynE8">PDP-8</a>. A PDP-8 program named SIM-14 allowed for simulating the PDP-14. </p> <h2 id="photos">Photos</h2> <ul><li><a href="http://www.chdickman.com/pdp14/">PDP-14</a></li> <li><a href="http://www.chdickman.com/modules/M740.jpg">PDP-14's M740 Instruction decoder module</a></li> <li><a href="http://www.chdickman.com/modules/M745.jpg">PDP-14's M745 PDP-8 Interface</a></li></ul> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/PDP-16/rcr65a01">PDP-16</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp14/DEC-14-GGZA-D_PDP14UM_Nov69.pdf">PDP-14 User's Manual</a></li> <li><a href="http://www.chdickman.com/pdp14">includes information about interfacing options</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Bell, C. Gordon; Mudge, J. Craig; McNamara, John E. (2014-05-12). Computer Engineering: A DEC View of Hardware Systems Design. Digital Press. ISBN 978-1-4832-2110-6. <a href="978-1-4832-2110-6" target="_blank">978-1-4832-2110-6</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>PDP 8/e, PDP 8/m & PDP 8/f Small Computer Handbook (PDF). Digital Equipment Corporation. 1973. p. 1-46. <a href="http://bitsavers.org/pdf/dec/pdp8/handbooks/Small_Computer_Handbook_1973.pdf" target="_blank">http://bitsavers.org/pdf/dec/pdp8/handbooks/Small_Computer_Handbook_1973.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Ball, Ken (2015-08-02). "The Dawn of the Programmable Logic Controller (PLC)". automation.com. Retrieved 2024-03-02. <a href="https://www.automation.com/en-us/articles/2015-2/the-dawn-of-the-programmable-logic-controller-plc" target="_blank">https://www.automation.com/en-us/articles/2015-2/the-dawn-of-the-programmable-logic-controller-plc</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>US3753243A, Ricketts, A.; Devault, A. & Doane, R. et al., "Programmable machine controller", issued 1973-08-14 <a href="https://patents.google.com/patent/US3753243A/en?oq=3753243" target="_blank">https://patents.google.com/patent/US3753243A/en?oq=3753243</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"DEC PDP-14 Industrial Controller". <a href="http://www.chdickman.com/pdp14" target="_blank">http://www.chdickman.com/pdp14</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Nineteen Fifty-Seven To The Present (PDF). Digital Equipment Corporation. 1975. <a href="http://s3data.computerhistory.org/pdp-1/dec.digital_1957_to_the_present_(1978).1957-1978.102630349.pdf" target="_blank">http://s3data.computerhistory.org/pdp-1/dec.digital_1957_to_the_present_(1978).1957-1978.102630349.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"DEC PDP-14 Industrial Controller". <a href="http://www.chdickman.com/pdp14" target="_blank">http://www.chdickman.com/pdp14</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"DEC PDP-14 Industrial Controller". <a href="http://www.chdickman.com/pdp14" target="_blank">http://www.chdickman.com/pdp14</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>"DEC PDP-14 Industrial Controller". <a href="http://www.chdickman.com/pdp14" target="_blank">http://www.chdickman.com/pdp14</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"DEC PDP-14 Industrial Controller". <a href="http://www.chdickman.com/pdp14" target="_blank">http://www.chdickman.com/pdp14</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Randall Brodzik (August 27, 2014). "Inside the competition for the first PLC". <a href="http://www.controleng.com/single-article/inside-the-competition-for-the-first-plc/2455e5713e5c2cf400fdccc5f35923be.html" target="_blank">http://www.controleng.com/single-article/inside-the-competition-for-the-first-plc/2455e5713e5c2cf400fdccc5f35923be.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Randall Brodzik (August 27, 2014). "Inside the competition for the first PLC". <a href="http://www.controleng.com/single-article/inside-the-competition-for-the-first-plc/2455e5713e5c2cf400fdccc5f35923be.html" target="_blank">http://www.controleng.com/single-article/inside-the-competition-for-the-first-plc/2455e5713e5c2cf400fdccc5f35923be.html</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> </ol>