Only dump memory initialization in icebox_vlog if present in ASC file, fixes #228

Signed-off-by: Clifford Wolf <clifford@clifford.at>

icebox/icebox_vlog.py

diff --git a/icebox/icebox_vlog.py b/icebox/icebox_vlog.py
index 184cb03..a2c7950 100755
--- a/icebox/icebox_vlog.py
+++ b/icebox/icebox_vlog.py
@@ -750,8 +750,9 @@
         text_func.append("SB_RAM40_4K%s%s #(" % ("NR" if negclk_rd else "", "NW" if negclk_wr else ""));
         text_func.append("  .READ_MODE(%d)," % ((1 if get_ram_config('CBIT_2') else 0) + (2 if get_ram_config('CBIT_3') else 0)));
         text_func.append("  .WRITE_MODE(%d)," % ((1 if get_ram_config('CBIT_0') else 0) + (2 if get_ram_config('CBIT_1') else 0)));
-        for i in range(16):
-            text_func.append("  .INIT_%X(256'h%s)%s" % (i, ic.ram_data[tile][i], "," if i < 15 else ""));
+        if tile in ic.ram_data:
+            for i in range(16):
+                text_func.append("  .INIT_%X(256'h%s)%s" % (i, ic.ram_data[tile][i], "," if i < 15 else ""));
         text_func.append(") ram40_%d_%d (" % tile);
         text_func.append("  .WADDR(%s),"  % get_ram_wire('WADDR', 10, 0))
         text_func.append("  .RADDR(%s),"  % get_ram_wire('RADDR', 10, 0))