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  13. 

  14. <div class="toc">
    15. 

  15. <div class="tocheader toctoggle" id="toc__header">Table of Contents</div>
    16. 

  16. <div id="toc__inside">
    17. 

  17. 

  18. <ul class="toc">
    19. 

  19. <li class="level1"><div class="li"><span class="li"><a href="#net_attribute_mini-howto" class="toc">net= attribute mini-HOWTO</a></span></div>
    20. 

  20. <ul class="toc">
    21. 

  21. <li class="level2"><div class="li"><span class="li"><a href="#what_is_the_net_attribute_used_for" class="toc">What is the net= attribute used for?</a></span></div></li>
    22. 

  22. <li class="level2"><div class="li"><span class="li"><a href="#what_is_the_format_of_the_net_attribute" class="toc">What is the format of the net= attribute?</a></span></div></li>
    23. 

  23. <li class="level2"><div class="li"><span class="li"><a href="#how_do_you_actually_use_the_net_attribute" class="toc">How do you actually use the net= attribute?</a></span></div></li>
    24. 

  24. <li class="level2"><div class="li"><span class="li"><a href="#caveats_bugs" class="toc">Caveats / Bugs</a></span></div></li>
    25. 

  25. <li class="level2"><div class="li"><span class="li"><a href="#example" class="toc">Example</a></span></div></li>
    26. 

  26. <li class="level2"><div class="li"><span class="li"><a href="#final_notes" class="toc">Final notes</a></span></div></li></ul>
    27. 

  27. </li></ul>
    28. 

  28. </div>
    29. 

  29. </div>
    30. 

  30. 

  31. 

  32. 

  33. <h1><a name="net_attribute_mini-howto" id="net_attribute_mini-howto">net= attribute mini-HOWTO</a></h1>
    34. 

  34. <div class="level1">
    35. 

  35. 

  36. <p>
    37. 

  37. by: Ales Hvezda
    38. 

  38. </p>
    39. 

  39. 

  40. <p>
    41. 

  41. This document is released under <a href="http://www.gnu.org/copyleft/fdl.html" class="urlextern" title="http://www.gnu.org/copyleft/fdl.html"  rel="nofollow">GFDL</a>
    42. 

  42. </p>
    43. 

  43. 

  44. <p>
    45. 

  45. October 2nd, 2003
    46. 

  46. </p>
    47. 

  47. 

  48. <p>
    49. 

  49. The information in this document is current as of 19991011.
    50. 

  50. </p>
    51. 

  51. 

  52. </div>
    53. 

  53. <!-- SECTION "net= attribute mini-HOWTO" [1-216] -->
    54. 

  54. <h2><a name="what_is_the_net_attribute_used_for" id="what_is_the_net_attribute_used_for">What is the net= attribute used for?</a></h2>
    55. 

  55. <div class="level2">
    56. 

  56. 

  57. <p>
    58. 

  58. The <strong><code>net=</code></strong> attribute is used to specify power, ground, and/or arbitrary nets in the gEDA system.<br/>
    59. 

  59.  The <strong><code>net=</code></strong> attribute is used instead some of the other systems of specifying power/ground (such as having power/ground pins on symbols or power boxes). Some devices have lots of power/ground pins and having all of these pins on the symbol would increase its size and make it unmanageable. The <strong><code>net=</code></strong> attribute is the power/ground specification of choice in the gEDA system because of its simplicity and versatility. Now having said all this, you can have power/ground pins on a symbol, but gnetlist will probably not recognize these nets connected to these pins as separate power/ground nets. Please keep this in mind as you draw symbols.
    60. 

  60. </p>
    61. 

  61. 

  62. </div>
    63. 

  63. <!-- SECTION "What is the net= attribute used for?" [217-1022] -->
    64. 

  64. <h2><a name="what_is_the_format_of_the_net_attribute" id="what_is_the_format_of_the_net_attribute">What is the format of the net= attribute?</a></h2>
    65. 

  65. <div class="level2">
    66. 

  66. 

  67. <p>
    68. 

  68. Attributes in gEDA are simple text items which are in the form <code>name=value</code>. All proper attributes follow this form. Attribute names are always lower case, but the value can be upper or lower case. gnetlist and friends are case sensitive. Typically net/signal names by default are upper case.<br/>
    69. 

  69.  Attribute can be attached to an object or in certain cases (like the <strong><code>net=</code></strong> attribute) can be free oating (not attached to anything). The free floating attributes are also called toplevel attributes.<br/>
    70. 

  70.  The <strong><code>net=</code></strong> attribute is a text item which takes on the following form: 
    71. 

  71. </p>
    72. 

  72. <pre class="code">net=signalname:pinname,pinname,pinname,...</pre>
    73. 

  73. 

  74. <p>
    75. 

  75. where:
    76. 

  76. </p>
    77. 

  77. <table class="inline">
    78. 

  78. 	<tr>
    79. 

  79. 		<td> <strong><code>net=</code></strong> </td><td> The attribute name (always the same, lowercase) </td>
    80. 

  80. 	</tr>
    81. 

  81. 	<tr>
    82. 

  82. 		<td> signalname </td><td> The signal or net being defines (like +5V, GND, etc&hellip;) </td>
    83. 

  83. 	</tr>
    84. 

  84. 	<tr>
    85. 

  85. 		<td> pinname </td><td> The pin name (or number) which is assigned to this signal/net (or pin names/numbers) </td>
    86. 

  86. 	</tr>
    87. 

  87. </table>
    88. 

  88. 

  89. <p>
    90. 

  90.  The signalname cannot contain the &quot;:&quot; character (since it is a delimiter). The pinname is the pin name (A1, P2, D1, etc&hellip;) or pin number (1, 2, 5, 13, etc&hellip;). The pinname cannot contain the &quot;,&quot; character (since it is also a delimiter). pinnames are typically the same sort of numbers/names like the <code>pin#=#</code> attribute (if you are familiar with that attribute).<br/>
    91. 

  91.  You can only have ONE signalname per <strong><code>net=</code></strong> attribute, but you can have as many pinnames/numbers as you want.
    92. 

  92. </p>
    93. 

  93. 

  94. </div>
    95. 

  95. <!-- SECTION "What is the format of the net= attribute?" [1023-2446] -->
    96. 

  96. <h2><a name="how_do_you_actually_use_the_net_attribute" id="how_do_you_actually_use_the_net_attribute">How do you actually use the net= attribute?</a></h2>
    97. 

  97. <div class="level2">
    98. 

  98. 

  99. <p>
    100. 

  100. You can place the <strong><code>net=</code></strong> attribute in several places. Here’s the list so far:
    101. 

  101. </p>
    102. 

  102. <ul>
    103. 

  103. <li class="level1"><div class="li"> Inside a symbol either as an attached attribute or an unattached attribute (toplevel attribute). Example which creates power/gnd nets: <strong><code>net=GND:7</code></strong> or <strong><code>net=+5V:14</code></strong></div>
    104. 

  104. </li>
    105. 

  105. <li class="level1"><div class="li"> Outside a symbol (which is instantiated on a schematic) attached as an attribute to override an existing <strong><code>net=</code></strong> created net/signal. Suppose a symbol has a <strong><code>net=GND:7</code></strong> inside it already; attaching this to the symbol: <strong><code>net=AGND:7</code></strong> overrides the GND net (on pin 7) calling it AGND and connects/associates it to pin 7.</div>
    106. 

  106. </li>
    107. 

  107. <li class="level1"><div class="li"> Outside or inside a symbol to connect a net to a visible pin automatically. This is still untested and still might have some undesirable (negative) side effects. Use with caution.</div>
    108. 

  108. </li>
    109. 

  109. <li class="level1"><div class="li"> Attached to one of those special power/gnd symbol (like vcc/gnd/vdd) and you can change what that symbol represents. You could change the ground symbol to create a net called DIGITAL GND without editing the symbol (<strong><code>net=DIGITAL_GND:1</code></strong>).<br/>
    110. 

  110.  In the current symbol (19991011) library there are symbols named <strong>vdd-1.sym</strong>, <strong>vcc-1.sym</strong>, <strong>vee-1.sym</strong>, etc&hellip; which do not have a <strong><code>net=</code></strong> attribute inside, so you must attach the <strong><code>net=</code></strong> attribute yourself (in the schematic).<br/>
    111. 

  111.  There also symbols named 5V-minus-1.sym, 12V-plus-1.sym, 9V-plus-1.sym, etc&hellip; which have the appropriate <strong><code>net=</code></strong> attribute in them already (can be overridden though). You can use these symbol as examples of how to use the <strong><code>net=</code></strong> attribute.<br/>
    112. 

  112. </div>
    113. 

  113. </li>
    114. 

  114. </ul>
    115. 

  115. 

  116. <p>
    117. 

  117. You can have as many <strong><code>net=</code></strong> attributes as you want. Just remember that <strong><code>net=</code></strong> attributes attached to the outside of a symbol override any equivalent internal (inside the symbol) <strong><code>net=</code></strong> attributes. If you run into a case where this doesn’t work, please let <strong>ahvezdaATgeda.seul.org</strong>. In fact, send any bug reports to that individual.
    118. 

  118. </p>
    119. 

  119. 

  120. </div>
    121. 

  121. <!-- SECTION "How do you actually use the net= attribute?" [2447-4387] -->
    122. 

  122. <h2><a name="caveats_bugs" id="caveats_bugs">Caveats / Bugs</a></h2>
    123. 

  123. <div class="level2">
    124. 

  124. 

  125. <p>
    126. 

  126. The <strong><code>net=</code></strong> attribute/mechanism is fairly new, so there are bound to be bugs (many bugs). Here are some of the identified issues:
    127. 

  127. </p>
    128. 

  128. <ul>
    129. 

  129. <li class="level1"><div class="li"> As of 19991011 almost all of the symbols in the standard library do not have the <strong><code>net=</code></strong> attribute or any other power/ground specifiers. Hopefully this will be updated sometime (any volunteers?).</div>
    130. 

  130. </li>
    131. 

  131. <li class="level1"><div class="li"> Attach a special power symbol (vcc/gnd) to a already named net will alias (rename) that net to the signalname specified in the <strong><code>net=</code></strong> attribute (in/attached to the vcc/gnd symbol). You can override this (so the reverse is true) by playing with the “net-naming-priority”. Be careful with this. There might be other “aliasing” issues which have not been identified yet.</div>
    132. 

  132. </li>
    133. 

  133. <li class="level1"><div class="li"> Creating a <strong><code>net=</code></strong> attribute which associates a signal name with a pin which is already visible on the symbol, is probably a bad idea. This does work, but all the ramifications have not been explored yet.</div>
    134. 

  134. </li>
    135. 

  135. <li class="level1"><div class="li"> It is probably a bad idea to have the same <strong><code>net=</code></strong> attribute attached several times. Ales has not formalized what happens in this case. Just remember that the <strong><code>net=</code></strong> attribute on the outside of a symbol should override the internal one.</div>
    136. 

  136. </li>
    137. 

  137. </ul>
    138. 

  138. 

  139. </div>
    140. 

  140. <!-- SECTION "Caveats / Bugs" [4388-5599] -->
    141. 

  141. <h2><a name="example" id="example">Example</a></h2>
    142. 

  142. <div class="level2">
    143. 

  143. 

  144. <p>
    145. 

  145. Here’s a schematic which uses standard symbols (note: the 7400 does not have the <strong><code>net=</code></strong> attribute inside yet). This schematic consists of a 7400 with the <strong><code>net=</code></strong> attributes attached for power and ground, One of the input pins grounded using a gnd symbol and the other at a logic one using the vcc symbol (with an attached <strong><code>net=</code></strong> attribute). One of the input net is named, but as you will see, the netname is replaced by the <strong><code>net=</code></strong> signal name (see above for more info on this). The output is pulled up with a pull up resistor which has power specified using the +5V symbol.<br/>
    146. 

  146.  
    147. 

  147. </p>
    148. 

  148. <table class="inline">
    149. 

  149. 	<tr>
    150. 

  150. 		<td> <a href="media/geda/net.jpg" class="media" target="_blank" title="geda:net.jpg"><img src="media/geda/net.jpg" class="media" alt="" /></a> </td>
    151. 

  151. 	</tr>
    152. 

  152. </table>
    153. 

  153. <pre class="code">v 19991011
    154. 

  154. C 38700 58100 1 0 0 7400-1.sym
    155. 

  155. {
    156. 

  156. T 39000 59000 5 10 1 1 0
    157. 

  157. uref=U100
    158. 

  158. T 38900 59500 5 10 1 1 0
    159. 

  159. net=GND:7
    160. 

  160. T 38900 59300 5 10 1 1 0
    161. 

  161. net=+5V:14
    162. 

  162. }
    163. 

  163. N 38700 58800 37400 58800 4
    164. 

  164. {
    165. 

  165. T 37600 58900 5 10 1 1 0
    166. 

  166. netname=NETLABEL
    167. 

  167. }
    168. 

  168. N 37400 58800 37400 59200 4
    169. 

  169. N 38700 58400 37400 58400 4
    170. 

  170. N 37400 58000 37400 58400 4
    171. 

  171. C 37300 57700 1 0 0 gnd-1.sym
    172. 

  172. C 37200 59200 1 0 0 vcc-1.sym
    173. 

  173. {
    174. 

  174. T 36800 59200 5 10 1 1 0
    175. 

  175. net=+5V:1
    176. 

  176. }
    177. 

  177. N 40000 58600 41600 58600 4
    178. 

  178. {
    179. 

  179. T 41200 58700 5 10 1 1 0
    180. 

  180. netname=OUTPUT
    181. 

  181. }
    182. 

  182. C 40700 58800 1 90 0 resistor-1.sym
    183. 

  183. {
    184. 

  184. T 40800 59200 5 10 1 1 0
    185. 

  185. uref=R1
    186. 

  186. }
    187. 

  187. N 40600 58800 40600 58600 4
    188. 

  188. N 40600 59900 40600 59700 4
    189. 

  189. C 40400 59900 1 0 0 5V-plus-1.sym</pre>
    190. 

  190. 

  191. <p>
    192. 

  192. <strong>gnetlist</strong> (using the geda netlist format) run using this sample schematic outputs this: 
    193. 

  193. </p>
    194. 

  194. <pre class="code">START header
    195. 

  195. 

  196. gEDA&#039;s netlist format
    197. 

  197. Created specifically for testing of gnetlist
    198. 

  198. 

  199. END header
    200. 

  200. 

  201. START components
    202. 

  202. 

  203. R1 device=RESISTOR
    204. 

  204. U100 device=7400
    205. 

  205. 

  206. END components
    207. 

  207. 

  208. START renamed-nets
    209. 

  209. 

  210. NETLABEL -&gt; +5V
    211. 

  211. 

  212. END renamed-nets
    213. 

  213. 

  214. START nets
    215. 

  215. 

  216. +5V : R1 2, U100 14, U100 1
    217. 

  217. GND : U100 7, U100 2
    218. 

  218. OUTPUT : R1 1, U100 3
    219. 

  219. 

  220. END nets</pre>
    221. 

  221. 

  222. <p>
    223. 

  223. Notice how NETLABEL was renamed (aliased to the +5V net).
    224. 

  224. </p>
    225. 

  225. 

  226. </div>
    227. 

  227. <!-- SECTION "Example" [5600-7377] -->
    228. 

  228. <h2><a name="final_notes" id="final_notes">Final notes</a></h2>
    229. 

  229. <div class="level2">
    230. 

  230. 

  231. <p>
    232. 

  232. Send all bugs to <strong>ahvezdaATgeda.seul.org</strong> or <strong>geda-devATgeda.seul.org</strong> (mailing list, please subscribe first). [I’m sure there’s more to say here] 
    233. 

  233. </p>
    234. 

  234. 

  235. </div>
    236. 

  236. <!-- SECTION "Final notes" [7378-] --></body>
    237. 

  237. </html>
    238. 

  238.