# BC100 CodeSys 3.5 **URL:** \ **Category:** CODESYS\ **Created:** [December 20, 2025, 2:39pm UTC](https://www.wago.community/t/bc100-codesys-3-5/2471 "2025-12-20T14:39:33Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![ledieujojo](https://avatars.discourse-cdn.com/v4/letter/l/8c91f0/32.png) [@ledieujojo](https://www.wago.community/u/ledieujojo)\ **Post date:** [December 20, 2025, 2:39pm UTC](https://www.wago.community/t/bc100-codesys-3-5/2471/1 "2025-12-20T14:39:33Z")
Hello, I am new to Codesys (V3.5 SP21 patch 2) and Wago PLCs. For this purpose, I purchased a basic controller 100, model 750-8001, along with two 753-430 and two 753-530 modules. I found it already configured with Wago Ethernet settings, including its IP address, and I installed the latest firmware version, which is 01.04.07(04). I was able to connect to the device via Codesys, download the program, but when trying to start the program, an error appears: “program start interlock,” which prevents me from proceeding further. It seems the issue is related to the device’s communication. Does anyone have any idea what I should do to get it working? ---
**Author:** ![seweryn](https://sea2.discourse-cdn.com/flex016/user_avatar/www.wago.community/seweryn/32/1900_2.png) [@seweryn](https://www.wago.community/u/seweryn)\ **Post date:** [December 22, 2025, 8:12am UTC](https://www.wago.community/t/bc100-codesys-3-5/2471/2 "2025-12-22T08:12:19Z")
Hello, it could be, that something is wrong with your program. Double check the program’s logic. Also, you can share your CodeSYS project here and we will take a look at it. ---
**Author:** ![Paul](https://avatars.discourse-cdn.com/v4/letter/p/bbe5ce/32.png) [@Paul](https://www.wago.community/u/Paul)\ **Post date:** [December 22, 2025, 8:38am UTC](https://www.wago.community/t/bc100-codesys-3-5/2471/3 "2025-12-22T08:38:40Z")
Hello, The “program start interlock” error indicates a discrepancy between the KBUS configuration declared in the program and the physical configuration behind your station head. You need to check the KBUS section in Codesys to verify the declaration of your cards. ---
**Author:** ![ledieujojo](https://avatars.discourse-cdn.com/v4/letter/l/8c91f0/32.png) [@ledieujojo](https://www.wago.community/u/ledieujojo)\ **Post date:** [December 22, 2025, 8:05pm UTC](https://www.wago.community/t/bc100-codesys-3-5/2471/4 "2025-12-22T20:05:02Z")
I did a little research—could the absence of an end module (750-600) be the root cause of the error? I have manually verified the hardware configuration, and everything appears correct. However, when connecting to the device, there is indeed a red triangle next to the Kbus. When I check the Kbus parameters under “Status,” I see highlighted red text indicating a configuration error. (I also have the I/O LED on my BC100 blinking red.) ---
**Author:** ![quenorha](https://sea2.discourse-cdn.com/flex016/user_avatar/www.wago.community/quenorha/32/429_2.png) [@quenorha](https://www.wago.community/u/quenorha)\ **Post date:** [December 23, 2025, 6:35am UTC](https://www.wago.community/t/bc100-codesys-3-5/2471/5 "2025-12-23T06:35:01Z")
Absolutely. Without a 750-600, or in case the K-bus is disrupted (not properly aligned for instance), it won’t run and you might have this kind of issue. What is your I/O LED Error code (check manual for meaning) ? ---
**Author:** ![ledieujojo](https://avatars.discourse-cdn.com/v4/letter/l/8c91f0/32.png) [@ledieujojo](https://www.wago.community/u/ledieujojo)\ **Post date:** [December 30, 2025, 12:18pm UTC](https://www.wago.community/t/bc100-codesys-3-5/2471/6 "2025-12-30T12:18:25Z")
I add a 750-600 at the end and now, everything is ok, the I/O led is green. In codesys the K-bus is ready and when I turn on my program all is good.