ram: adjusted tap distance calculation

Signed-off-by: braydenl9988 <[email protected]>

Author: braydenlouie

src/ram/src/ram.cpp

@@ -571,11 +571,14 @@ void RamGen::generate(const int bytes_per_word,
       auto tapcell_layout = generateTapColumn(word_count, 0);
       ram_grid.insertLayout(std::move(tapcell_layout), 0); 
     } else {
-      int nearest_tap = 0;
+      // needed this calculation so first cells have right distance
+      int nearest_tap = (max_tap_dist / ram_grid.getWidth()) * ram_grid.getLayoutWidth(0);
       int tapcell_count = 0;
+      // x distance between transistor and tapcell means 2x distance between tapcells
+      max_tap_dist *= 2; 
       // iterates through each of the columns 
       for (int col = 0; col < ram_grid.numLayouts(); ++col) {
-        if (nearest_tap >= max_tap_dist) { 
+        if (nearest_tap + ram_grid.getLayoutWidth(col) >= max_tap_dist) { 
           //if the nearest_tap is too far, generate tap column
           auto tapcell_layout = generateTapColumn(word_count, tapcell_count);
           ram_grid.insertLayout(std::move(tapcell_layout), col);
@@ -585,7 +588,13 @@ void RamGen::generate(const int bytes_per_word,
         } 
         nearest_tap += ram_grid.getLayoutWidth(col);
       }
+      // check for last column in the grid
+      if (nearest_tap >= max_tap_dist / 2) {
+        auto tapcell_layout = generateTapColumn(word_count, tapcell_count);
+        ram_grid.addLayout(std::move(tapcell_layout));
+      }
     } 
+
   }  
 
   ram_grid.gridInit();

src/ram/src/ram.tcl

@@ -52,13 +52,14 @@ proc generate_ram_netlist { args } {
   if { [info exists keys(-tapcell)] } {
     if { [info exists keys(-max_tap_dist)] } {
       set max_tap_dist $keys(-max_tap_dist)
-      set max_tap_dist [expr $max_tap_dist * 1000]
+      set max_tap_dist [ord::microns_to_dbu $max_tap_dist]
     } else {
       utl::error RAM 21 "The -max_tap_dist argument must be specified with tapcell."
     }
     set tapcell $keys(-tapcell)
   } else {
-    utl::info RAM 22 "No tapcell is specified. The generated layout may not pass Design Rule Checks."
+    utl::info RAM 22 "No tapcell is specified.
+        The generated layout may not pass Design Rule Checks."
   }
 
   ram::generate_ram_netlist_cmd $bytes_per_word $word_count $storage_cell \

src/ram/test/make_8x8.tcl

@@ -20,7 +20,7 @@ generate_ram \
   -filler_cells {sky130_fd_sc_hd__fill_1 sky130_fd_sc_hd__fill_2 \
     sky130_fd_sc_hd__fill_4 sky130_fd_sc_hd__fill_8} \
   -tapcell sky130_fd_sc_hd__tap_1 \
-  -max_tap_dist 30
+  -max_tap_dist 15 
 
 set lef_file [make_result_file make_8x8.lef]
 write_abstract_lef $lef_file