Added the "isosub" to the cifinput and cifoutput sections, mapping
it to the "substrate cut" (GDS 81:53) layer.  This allows substrate
regions to extract independently.  Note:  Currently this may require
copying the "isosub" layer up through the entire hierarchy to the
top level for the extraction to work correctly, pending a commit of
ongoing work to enhance the substrate extraction method in magic.

VERSION

diff --git a/VERSION b/VERSION
index da0f58a..45dd586 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.0.189
+1.0.191

sky130/magic/sky130.tech

diff --git a/sky130/magic/sky130.tech b/sky130/magic/sky130.tech
index 626abf2..ba24557 100644
--- a/sky130/magic/sky130.tech
+++ b/sky130/magic/sky130.tech
@@ -755,6 +755,13 @@
 	calma	64 13
 
 #----------------------------------------------------------------
+# SUBCUT
+#----------------------------------------------------------------
+
+ layer SUBCUT	isosub
+	calma	81 53
+
+#----------------------------------------------------------------
 # NWELL
 #----------------------------------------------------------------
 
@@ -2368,6 +2375,9 @@
  layer dnwell DNWELL
  labels DNWELL
 
+ layer isosub SUBCUT
+ labels SUBCUT
+
  layer npn DNWELL
  and-not NWELL,nwelcheck
  and NPNID
@@ -3870,6 +3880,7 @@
  calma NWELL 64 20
  calma DIFF 65 20
  calma DNWELL 64 18
+ calma SUBCUT 81 53
  calma PWRES 64 13
  calma TAP  65 44
  # LVTN
@@ -4996,8 +5007,6 @@
 
  substrate *ppdiff,*mvppdiff,space/w,pwell well $SUB -dnwell,isosub
 
-# Layer resistance: Use document xp018-PDS-v4_2_1.pdf
-
 # Resistances are in milliohms per square
 # Optional 3rd argument is the corner adjustment fraction
 # Device values come from trtc.cor (typical corner)