diff --git a/hw/ip/rom_ctrl/util/mem.py b/hw/ip/rom_ctrl/util/mem.py
index be914d0..1f96eeb 100644
--- a/hw/ip/rom_ctrl/util/mem.py
+++ b/hw/ip/rom_ctrl/util/mem.py
@@ -6,10 +6,10 @@
 import re
 import subprocess
 import tempfile
-from typing import BinaryIO, IO, List, Optional, TextIO, Tuple
+from typing import Any, BinaryIO, Dict, IO, List, Optional, TextIO, Tuple
 
 from elftools.elf.elffile import ELFFile  # type: ignore
-from util.design.secded_gen import ecc_encode_some  # type: ignore
+from util.design.secded_gen import ecc_encode_some, load_secded_config  # type: ignore
 
 
 class MemChunk:
@@ -47,20 +47,21 @@
                 toks.append(f'{word:0{word_chars}X}')
             outfile.write(' '.join(toks) + '\n')
 
-    def add_ecc32(self) -> None:
+    def add_ecc32(self, config: Dict[str, Any]) -> None:
         '''Add ECC32 integrity bits
 
         This extends the input words (which are assumed to be 32-bit) by 7
         bits, to make 39-bit words.
 
         '''
-        self.words = ecc_encode_some('inv_hsiao', 32, self.words)[0]
+        self.words = ecc_encode_some(config, 'inv_hsiao', 32, self.words)[0]
 
 
 class MemFile:
     def __init__(self, width: int, chunks: List[MemChunk]):
         self.width = width
         self.chunks = chunks
+        self.config = load_secded_config()
 
     def __str__(self) -> str:
         return ('MemFile(width={}, chunks_len={})'
@@ -319,7 +320,7 @@
         '''
         assert self.width <= 32
         for chunk in self.chunks:
-            chunk.add_ecc32()
+            chunk.add_ecc32(self.config)
         self.width = 39
 
     def collisions(self) -> List[Tuple[int, int]]:
diff --git a/hw/ip/rom_ctrl/util/scramble_image.py b/hw/ip/rom_ctrl/util/scramble_image.py
index fd5c8c6..e4f6bb4 100755
--- a/hw/ip/rom_ctrl/util/scramble_image.py
+++ b/hw/ip/rom_ctrl/util/scramble_image.py
@@ -13,7 +13,7 @@
 from Crypto.Hash import cSHAKE256
 
 from mem import MemChunk, MemFile
-from util.design.secded_gen import ecc_encode_some  # type: ignore
+from util.design.secded_gen import ecc_encode_some, load_secded_config  # type: ignore
 
 ROM_BASE_WORD = 0x8000 // 4
 ROM_SIZE_WORDS = 8192
@@ -285,6 +285,7 @@
         self.nonce = nonce
         self.key = key
         self.rom_size_words = rom_size_words
+        self.config = load_secded_config()
 
         self._addr_width = (rom_size_words - 1).bit_length()
 
@@ -504,7 +505,7 @@
                 w39 = w32 | (chk_bits << 32)
                 clr39 = self.unscramble_word(39, log_addr, w39)
                 clr32 = clr39 & mask32
-                exp39 = ecc_encode_some('inv_hsiao', 32, [clr32])[0][0]
+                exp39 = ecc_encode_some(self.config, 'inv_hsiao', 32, [clr32])[0][0]
                 if clr39 != exp39:
                     # The checksum doesn't match. Excellent!
                     found_mismatch = True
diff --git a/util/design/gen-flash-img.py b/util/design/gen-flash-img.py
index 36d1c66..64bc765 100755
--- a/util/design/gen-flash-img.py
+++ b/util/design/gen-flash-img.py
@@ -11,12 +11,13 @@
 import math
 import re
 from pathlib import Path
+from typing import Dict, Any
 
 import secded_gen
 
 
-def _add_intg_ecc(in_val: int) -> str:
-    result, m = secded_gen.ecc_encode("hamming", 64, in_val)
+def _add_intg_ecc(config: Dict[str, Any], in_val: int) -> str:
+    result, m = secded_gen.ecc_encode(config, "hamming", 64, in_val)
 
     m_nibbles = math.ceil(m / 4)
     result = format(result, '0' + str(16 + m_nibbles) + 'x')
@@ -25,8 +26,8 @@
     return result[1:]
 
 
-def _add_reliability_ecc(in_val: int) -> str:
-    result, m = secded_gen.ecc_encode("hamming", 68, in_val)
+def _add_reliability_ecc(config: Dict[str, Any], in_val: int) -> str:
+    result, m = secded_gen.ecc_encode(config, "hamming", 68, in_val)
 
     m_nibbles = math.ceil((68 + m) / 4)
     result = format(result, '0' + str(m_nibbles) + 'x')
@@ -50,6 +51,8 @@
     # search only for lines that contain data, skip all other comments
     result = re.findall(r"^@.*$", vmem_orig, flags=re.MULTILINE)
 
+    config = secded_gen.load_secded_config()
+
     output = []
     for line in result:
         items = line.split()
@@ -58,8 +61,8 @@
             if re.match(r"^@", item):
                 result += item
             else:
-                data_w_intg_ecc = _add_intg_ecc(int(item, 16))
-                full_ecc = _add_reliability_ecc(int(data_w_intg_ecc, 16))
+                data_w_intg_ecc = _add_intg_ecc(config, int(item, 16))
+                full_ecc = _add_reliability_ecc(config, int(data_w_intg_ecc, 16))
                 result += f' {full_ecc}'
 
         # add processed element to output
diff --git a/util/design/secded_gen.py b/util/design/secded_gen.py
index 5b08aa4..9276ee2 100755
--- a/util/design/secded_gen.py
+++ b/util/design/secded_gen.py
@@ -19,7 +19,7 @@
 import random
 import hjson
 import subprocess
-from typing import List, Tuple
+from typing import Any, Dict, List, Tuple
 from pathlib import Path
 
 COPYRIGHT = """// Copyright lowRISC contributors.
@@ -137,7 +137,7 @@
     if dec:
         for j in range(m):
             fanin_masks[j] += 1 << (k + j)
-    return fanin_masks
+    return tuple(fanin_masks)
 
 
 def print_secded_enum_and_util_fns(cfgs):
@@ -356,9 +356,8 @@
     return error
 
 
-def _ecc_pick_code(codetype: str, k: int) -> Tuple[int, List[int], int]:
+def _ecc_pick_code(config: Dict[str, Any], codetype: str, k: int) -> Tuple[int, List[int], int]:
     # first check to see if bit width is supported among configuration
-    config = hjson.load(SECDED_CFG_PATH.open())
 
     codes = None
     bitmasks = None
@@ -403,11 +402,10 @@
     return codeword
 
 
-@functools.lru_cache(maxsize = 1024)
-def ecc_encode(codetype: str, k: int, dataword: int) -> Tuple[int, int]:
+def ecc_encode(config: Dict[str, Any], codetype: str, k: int, dataword: int) -> Tuple[int, int]:
     log.info(f"Encoding ECC for {hex(dataword)}")
 
-    m, bitmasks, invert = _ecc_pick_code(codetype, k)
+    m, bitmasks, invert = _ecc_pick_code(config, codetype, k)
     codeword = _ecc_encode(k, m, bitmasks, invert, dataword)
 
     # Debug printouts
@@ -416,10 +414,11 @@
     return int(codeword, 2), m
 
 
-def ecc_encode_some(codetype: str,
+def ecc_encode_some(config: Dict[str, Any],
+                    codetype: str,
                     k: int,
                     datawords: int) -> Tuple[List[int], int]:
-    m, bitmasks, invert = _ecc_pick_code(codetype, k)
+    m, bitmasks, invert = _ecc_pick_code(config, codetype, k)
     codewords = [int(_ecc_encode(k, m, bitmasks, invert, w), 2)
                  for w in datawords]
     return codewords, m
@@ -901,6 +900,10 @@
         f.write(outstr)
 
 
+def load_secded_config() -> Dict[str, Any]:
+    return hjson.load(SECDED_CFG_PATH.open())
+
+
 def main():
     parser = argparse.ArgumentParser(
         prog="secded_gen",