nangate45: update pin pitch to 280nm / update config file for generation

Signed-off-by: Arthur Koucher <[email protected]>

Author: AcKoucher

flow/platforms/nangate45/fakeram.cfg

@@ -2,6 +2,20 @@
 # https://github.com/bespoke-silicon-group/bsg_fakeram.git
 # Using the following branch to correct bugs:
 # https://github.com/AcKoucher/bsg_fakeram.git nangate45 branch
+#
+# Not all fakerams' .lef/.lib we use in nangate45 designs were generated
+# using the default snapHeight specified in this .cfg, because the height
+# computed by the generator would result in not having enough available
+# tracks for the number of pins.
+#
+# For the exceptions below, we used a manually tuned height:
+#
+#   fakeram45_32x64     snapHeight_nm = 62000
+#   fakeram45_64x62     snapHeight_nm = 60500
+#   fakeram45_64x64     snapHeight_nm = 62200
+#   fakeram45_64x96     snapHeight_nm = 44700
+#   fakeram45_64x124    snapHeight_nm = 112600
+#   fakeram45_128x256   snapHeight_nm = 223900
 {
   # The process node. This is used to tell cacti what technology to use when
   # estimating power, performance and area numbers.
@@ -19,10 +33,9 @@
   # The minimum pin pitch for signal pins (all pins will have a pitch that is a
   # multiple of this pitch). The first pin will be a multiple of this pitch from
   # the bottom edge of the macro too.
-  #
-  # If the multiple is not even, we'll end up generating macros we can't snap to
-  # align with the trackgrid.
-  "pinPitch_nm": 140,
+  # The pin pitch must be a multiple of the track-grid pitch, otherwise we'll
+  # end up generating macros we can't snap to align with the latter.
+  "pinPitch_nm": 280,
 
   # Optional: snap the width and height of the sram to a multiple value.
   "snapWidth_nm":  190,