From 5197222fbfc70704488561db605fa6e0db5dd543 Mon Sep 17 00:00:00 2001
From: Meisam Bahadori <meisambahadori@gmail.com>
Date: Thu, 30 Jul 2026 14:04:36 +0200
Subject: [PATCH] pa-243

---
 src/frontend/snp2va.c   | 22 +++++++++++++---------
 src/frontend/snp2va.cpp | 22 +++++++++++++---------
 2 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/src/frontend/snp2va.c b/src/frontend/snp2va.c
index 1c8aa120c..41c516ebd 100644
--- a/src/frontend/snp2va.c
+++ b/src/frontend/snp2va.c
@@ -853,13 +853,17 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
     fprintf(fo, "// Generated by pre_snp from %s\n", snpfile);
     fprintf(fo, "// %d-port, %d common poles; structured realization (%d laplace_nd filters, AC + transient).\n",
             N, Np, nfilt);
+    /* E-243: an explicit `ref` reference terminal (last port), so every branch is
+     * V(pi,ref)/I(pi,ref) and the instance line -- `N1 p1..pN ref model` -- is
+     * IDENTICAL to the native `nport` device (tie ref to 0 for a ground-referenced
+     * Touchstone block). */
     fprintf(fo, "module %s(", module);
     for (i = 0; i < N; i++) fprintf(fo, "%sp%d", i?", ":"", i+1);
-    fprintf(fo, ");\n    inout ");
+    fprintf(fo, ", ref);\n    inout ");
     for (i = 0; i < N; i++) fprintf(fo, "%sp%d", i?", ":"", i+1);
-    fprintf(fo, ";\n    electrical ");
+    fprintf(fo, ", ref;\n    electrical ");
     for (i = 0; i < N; i++) fprintf(fo, "%sp%d", i?", ":"", i+1);
-    fprintf(fo, ";\n");
+    fprintf(fo, ", ref;\n");
     /* variable declarations */
     for (c = 0; c < nchan; c++) {
         if (chMx[c]==0.0) continue;
@@ -881,20 +885,20 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
                 int first=1; fprintf(fo, "        g%d_%d = ", c, m);
                 for (j=0;j<N;j++){ double v=chV[c][j*ch_r[c]+m];
                     if (fabs(v)>1e-30){ term_sep(fo,&first);
-                        if (ch_kind[c]==0) fprintf(fo,"(%.12g)*V(p%d)",v,j+1); else fprintf(fo,"(%.12g)*ddt(V(p%d))",v,j+1); } }
+                        if (ch_kind[c]==0) fprintf(fo,"(%.12g)*V(p%d,ref)",v,j+1); else fprintf(fo,"(%.12g)*ddt(V(p%d,ref))",v,j+1); } }
                 if (first) fprintf(fo,"0.0"); fprintf(fo,";\n");
             }
             continue;
         }
         int sc=ch_sec[c], kk=sc_pole[sc];
         if (!ch_lr[c]) {                            /* dense: one laplace_nd per input port */
-            for (j=0;j<N;j++){ fprintf(fo,"        w%d_%d = laplace_nd(V(p%d), ", c, j, j+1);
+            for (j=0;j<N;j++){ fprintf(fo,"        w%d_%d = laplace_nd(V(p%d,ref), ", c, j, j+1);
                 emit_filter(fo, P[kk], sc_kind[sc]); fprintf(fo,");\n"); }
         } else {                                    /* low-rank: r combined inputs, each filtered once */
             for (m=0;m<ch_r[c];m++){
                 int first=1; fprintf(fo,"        u%d_%d = ", c, m);
                 for (j=0;j<N;j++){ double v=chV[c][j*ch_r[c]+m];
-                    if (fabs(v)>1e-30){ term_sep(fo,&first); fprintf(fo,"(%.12g)*V(p%d)",v,j+1); } }
+                    if (fabs(v)>1e-30){ term_sep(fo,&first); fprintf(fo,"(%.12g)*V(p%d,ref)",v,j+1); } }
                 if (first) fprintf(fo,"0.0"); fprintf(fo,";\n");
                 fprintf(fo,"        h%d_%d = laplace_nd(u%d_%d, ", c, m, c, m);
                 emit_filter(fo, P[kk], sc_kind[sc]); fprintf(fo,");\n");
@@ -903,7 +907,7 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
     }
     /* output currents */
     for (i = 0; i < N; i++) {
-        int first = 1; fprintf(fo, "        I(p%d) <+ ", i+1);
+        int first = 1; fprintf(fo, "        I(p%d,ref) <+ ", i+1);
         for (c = 0; c < nchan; c++) {
             if (chMx[c]==0.0) continue;
             if (ch_lr[c]) {
@@ -914,8 +918,8 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
                 double thr = tol_drop*chMx[c];
                 for (j=0;j<N;j++){ double w=chW[c][i*N+j];
                     if (fabs(w)>thr){ term_sep(fo,&first);
-                        if (ch_kind[c]==0)      fprintf(fo,"(%.12g)*V(p%d)",w,j+1);
-                        else if (ch_kind[c]==1) fprintf(fo,"(%.12g)*ddt(V(p%d))",w,j+1);
+                        if (ch_kind[c]==0)      fprintf(fo,"(%.12g)*V(p%d,ref)",w,j+1);
+                        else if (ch_kind[c]==1) fprintf(fo,"(%.12g)*ddt(V(p%d,ref))",w,j+1);
                         else                    fprintf(fo,"(%.12g)*w%d_%d",w,c,j); } }
             }
         }
diff --git a/src/frontend/snp2va.cpp b/src/frontend/snp2va.cpp
index 1c8aa120c..41c516ebd 100644
--- a/src/frontend/snp2va.cpp
+++ b/src/frontend/snp2va.cpp
@@ -853,13 +853,17 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
     fprintf(fo, "// Generated by pre_snp from %s\n", snpfile);
     fprintf(fo, "// %d-port, %d common poles; structured realization (%d laplace_nd filters, AC + transient).\n",
             N, Np, nfilt);
+    /* E-243: an explicit `ref` reference terminal (last port), so every branch is
+     * V(pi,ref)/I(pi,ref) and the instance line -- `N1 p1..pN ref model` -- is
+     * IDENTICAL to the native `nport` device (tie ref to 0 for a ground-referenced
+     * Touchstone block). */
     fprintf(fo, "module %s(", module);
     for (i = 0; i < N; i++) fprintf(fo, "%sp%d", i?", ":"", i+1);
-    fprintf(fo, ");\n    inout ");
+    fprintf(fo, ", ref);\n    inout ");
     for (i = 0; i < N; i++) fprintf(fo, "%sp%d", i?", ":"", i+1);
-    fprintf(fo, ";\n    electrical ");
+    fprintf(fo, ", ref;\n    electrical ");
     for (i = 0; i < N; i++) fprintf(fo, "%sp%d", i?", ":"", i+1);
-    fprintf(fo, ";\n");
+    fprintf(fo, ", ref;\n");
     /* variable declarations */
     for (c = 0; c < nchan; c++) {
         if (chMx[c]==0.0) continue;
@@ -881,20 +885,20 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
                 int first=1; fprintf(fo, "        g%d_%d = ", c, m);
                 for (j=0;j<N;j++){ double v=chV[c][j*ch_r[c]+m];
                     if (fabs(v)>1e-30){ term_sep(fo,&first);
-                        if (ch_kind[c]==0) fprintf(fo,"(%.12g)*V(p%d)",v,j+1); else fprintf(fo,"(%.12g)*ddt(V(p%d))",v,j+1); } }
+                        if (ch_kind[c]==0) fprintf(fo,"(%.12g)*V(p%d,ref)",v,j+1); else fprintf(fo,"(%.12g)*ddt(V(p%d,ref))",v,j+1); } }
                 if (first) fprintf(fo,"0.0"); fprintf(fo,";\n");
             }
             continue;
         }
         int sc=ch_sec[c], kk=sc_pole[sc];
         if (!ch_lr[c]) {                            /* dense: one laplace_nd per input port */
-            for (j=0;j<N;j++){ fprintf(fo,"        w%d_%d = laplace_nd(V(p%d), ", c, j, j+1);
+            for (j=0;j<N;j++){ fprintf(fo,"        w%d_%d = laplace_nd(V(p%d,ref), ", c, j, j+1);
                 emit_filter(fo, P[kk], sc_kind[sc]); fprintf(fo,");\n"); }
         } else {                                    /* low-rank: r combined inputs, each filtered once */
             for (m=0;m<ch_r[c];m++){
                 int first=1; fprintf(fo,"        u%d_%d = ", c, m);
                 for (j=0;j<N;j++){ double v=chV[c][j*ch_r[c]+m];
-                    if (fabs(v)>1e-30){ term_sep(fo,&first); fprintf(fo,"(%.12g)*V(p%d)",v,j+1); } }
+                    if (fabs(v)>1e-30){ term_sep(fo,&first); fprintf(fo,"(%.12g)*V(p%d,ref)",v,j+1); } }
                 if (first) fprintf(fo,"0.0"); fprintf(fo,";\n");
                 fprintf(fo,"        h%d_%d = laplace_nd(u%d_%d, ", c, m, c, m);
                 emit_filter(fo, P[kk], sc_kind[sc]); fprintf(fo,");\n");
@@ -903,7 +907,7 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
     }
     /* output currents */
     for (i = 0; i < N; i++) {
-        int first = 1; fprintf(fo, "        I(p%d) <+ ", i+1);
+        int first = 1; fprintf(fo, "        I(p%d,ref) <+ ", i+1);
         for (c = 0; c < nchan; c++) {
             if (chMx[c]==0.0) continue;
             if (ch_lr[c]) {
@@ -914,8 +918,8 @@ int snp2va_convert(const char *snpfile, const char *vafile, const char *module,
                 double thr = tol_drop*chMx[c];
                 for (j=0;j<N;j++){ double w=chW[c][i*N+j];
                     if (fabs(w)>thr){ term_sep(fo,&first);
-                        if (ch_kind[c]==0)      fprintf(fo,"(%.12g)*V(p%d)",w,j+1);
-                        else if (ch_kind[c]==1) fprintf(fo,"(%.12g)*ddt(V(p%d))",w,j+1);
+                        if (ch_kind[c]==0)      fprintf(fo,"(%.12g)*V(p%d,ref)",w,j+1);
+                        else if (ch_kind[c]==1) fprintf(fo,"(%.12g)*ddt(V(p%d,ref))",w,j+1);
                         else                    fprintf(fo,"(%.12g)*w%d_%d",w,c,j); } }
             }
         }