From f174e5b83d4c41c888f015a083ccb8888bd2eca6 Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@koefferlein.de>
Date: Tue, 17 Dec 2019 20:29:37 +0100
Subject: [PATCH] Updated documentation

---
 src/lay/lay/doc/about/drc_ref_global.xml |  1 +
 src/lay/lay/doc/manual/lvs_connect.xml   | 52 ++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/src/lay/lay/doc/about/drc_ref_global.xml b/src/lay/lay/doc/about/drc_ref_global.xml
index 11f97782c..5d22e240b 100644
--- a/src/lay/lay/doc/about/drc_ref_global.xml
+++ b/src/lay/lay/doc/about/drc_ref_global.xml
@@ -234,6 +234,7 @@ See <a href="/about/drc_ref_netter.xml#connect_global">Netter#connect_global</a>
 <a name="connect_implicit"/><p>Usage:</p>
 <ul>
 <li><tt>connect_implicit(label_pattern)</tt></li>
+<li><tt>connect_implicit(cell_pattern, label_pattern)</tt></li>
 </ul>
 <p>
 See <a href="/about/drc_ref_netter.xml#connect_implicit">Netter#connect_implicit</a> for a description of that function.
diff --git a/src/lay/lay/doc/manual/lvs_connect.xml b/src/lay/lay/doc/manual/lvs_connect.xml
index e47efff0e..2fb0ff02c 100644
--- a/src/lay/lay/doc/manual/lvs_connect.xml
+++ b/src/lay/lay/doc/manual/lvs_connect.xml
@@ -131,4 +131,56 @@ connect(metal2, metal2_labels)</pre>
   opens may pass unnoticed.
   </p>
 
+  <p>
+  You can include labels of a certain class in a "connect_implicit" statement
+  using glob-style pattern:
+  </p>
+
+  <pre>connect_implicit("VDD*")</pre>
+
+  <p>
+  This will connect all nets labelled with "VDD1" for example or those labelled
+  with "VDD_5V". However, this statement will only connect "VDD1" with "VDD1",
+  <b>not</b> nets with different labels. I.e. it will not connect "VDD1" with "VDD2"
+  labels.
+  </p>
+
+  <p>
+  "connect_implicit" can be present multiple times. Each statement extends the
+  choice of labels which will be connected.
+  </p>
+
+  <p>
+  The standard method "connect_implicit" will only act on top-level cells.
+  However, sometimes the construction of certain library cells requires 
+  connecting nets inside subcells. For example, memory cells are often made
+  in a way that their common rails are exposed on different sides but 
+  not connected internally. Formally, those cells need to be described by
+  circuits with multiple pins in the schematic. As the cells are only used
+  in certain contexts where these rails are connected, it's sufficient to 
+  specify a single pin and connect the rails inside the subcells if labelled
+  properly. The following statement will connect all nets labelled with "VDD"
+  from the "MEMCELL" subcell:
+  </p>
+
+  <pre>connect_implicit("MEMCELL", "VDD")</pre>
+
+  <p>
+  If MEMCELL is the top cell, the single-argument, unspecific "connect_implicit"
+  rule is applied, unless no such rule is given. In other words: the unspecific
+  rule has priority for the top cell.
+  </p>
+
+  <p>
+  The cell argument can be a glob-style pattern. In this case, the rule is
+  applied to all matching cells. Again, the "connect_implicit" rule may be 
+  given multiple times. In this case, all matching occurances act together.
+  </p>
+
+  <p>
+  The "connect_implicit" statements must be given before the netlist is 
+  extracted. Typically this happens before or shortly after "connect"
+  statements.
+  </p>
+
 </doc>