ImportError: Missing 'lef_rom_interconnect' in stable version's OpenRAM tech module

[OsFlora]

Describe the bug
When compiling SRAM using the command line, the following error occurs:
from openram.tech import drc, layer, parameter, lef_rom_interconnect
ImportError: cannot import name 'lef_rom_interconnect' from 'openram.tech'

Version
OpenRAM stable version (default clone)

To Reproduce
I checked the latest version of the repo, and I found that the keyword ' lef_rom_interconnect' has been deleted, while it still appears on the stable version, which leads to the bug on the default clone.

Expected behavior
Please take a look, thanks

[sheyestherrr]

I also encountered this problem today.

[buchtawill]

I also had the issue, the temporary fix for me was to comment out
from .rom_bank import * in OpenRAM/compiler/modules/__init__.py since I only care about SRAM generation currently

[vikashpatel24]

🛠️ Fix for Missing lef_rom_interconnect in tech.py

Go to your technology folder (for example):

OpenRAM/technology/freepdk45/tech/

and open the file:

tech/tech.py

Then add the following line above the layer_indices dictionary (or anywhere before it’s used):

lef_rom_interconnect = ["m1", "m2", "m3", "m4", "m5"]

---

📄 Example — tech.py after modification

###################################################
# Interconnect stacks
###################################################

poly_stack = ("poly", "contact", "m1")
active_stack = ("active", "contact", "m1")
m1_stack = ("m1", "via1", "m2")
m2_stack = ("m2", "via2", "m3")
m3_stack = ("m3", "via3", "m4")

# Added to support ROM generation
lef_rom_interconnect = ["m1", "m2", "m3", "m4", "m5"]

layer_indices = {
    "poly": 0,
    "active": 0,
    "m1": 1,
    "m2": 2,
    "m3": 3,
    "m4": 4
}

# The FEOL stacks get us up to m1
feol_stacks = [
    poly_stack,
    active_stack
]

# The BEOL stacks are m1 and up
beol_stacks = [
    m1_stack,
    m2_stack,
    m3_stack
]

layer_stacks = feol_stacks + beol_stacks

preferred_directions = {
    "poly": "V",
    "active": "V",
    "m1": "H",
    "m2": "V",
    "m3": "H",
    "m4": "V"
}

---

✅ Reason for this change:

• Defines lef_rom_interconnect to specify metal layers used for ROM routing.
• Prevents errors during ROM generation in OpenRAM.
• Keeps the technology file structure consistent across technologies.

[buchtawill]

Hi @vikashpatel24
Thank you for the fix. Could you possibly open a pull request with this fix so the maintainers can merge it for the default freepdk45 and close this issue?