Extension cable from C7-621?

[e5frog 0]

Hey. 

I wonder if the DSUB 15pin cable between the C7-621 and the extension module (Simatic S7, 6ES7 621-1AD00-6AE3) is a plain straight 1:1 cable or if there's anything special about it? 
Want to replace it since I have various problems and the cable bends back and forth every time the hatch opens (display part in lid, the rest in the cabinet). 

It's a pretty short cable, less than 0.5m, I'm also guessing it needs to be of limited length. 

I haven't found any information at all searching for it. 

Hope You can help. 

[sigmadelta 5]

Unfortunately, there is no information about the pin configuration that I can find.

I found a non-working IM 621 on ebay with the cable for 10 euro (plus shipping):

https://www.ebay.co.uk/itm/Siemens-Simatic-S7-6ES7-621-1AD00-6AE3-993gr-RA-2-9kg/153546712587?hash=item23c018e60b:g:aNcAAOSwPdNdF0Q1

I would consider upgrading this C7-621 to a S7-1500 and Comfort HMI if you plan to keep this machine for a long time.