The least expensive one-time solution would probably purchase a converter.

I am not connected with nor do I know anything about this product other than what the brochure says.  It sounds like it solves your HDLC en/decryption problem.

Luxcom EM-HDCL-0-2-1-0 

If you are going to make many of these PLC based HDLC diagnostic systems, you will want to invest the time to develop the logic in the PLC to handle the de/encryption.

LilManAndrew

Hi All,

I'm looking to establish an interface between a diagnostic system and my PLC (CPU-1214C).

The diagnostic system will poll the PLC via an HDLC encoded RS485 serial connection.

My main issue is that I haven't been able to find a simple solution to receive, process, and send back HDLC encoded information.

I have a CM-1241-Rs422/485 module, so if there is no simpler solution I can probably manually code the HDLC functionality (a nightmare for my limited knowledge).

Any help or advice would be greatly appreciated! Thanks

huggy_d1

If you are going to make many of these PLC based HDLC diagnostic systems, you will want to invest the time to develop the logic in the PLC to handle the de/encryption. 

It is not possible to develop a HDLC driver for a S7-1200 CM, as HDLC does not use an 11 bit frame for each character. You need a gateway.

Regards,
Kaulquappe