Encoder failure detect

Hello experts. I want to write code that detects encoder failure
at high speeds. Incremental encoder TTL 1024. To check, I took
out the encoder wire A, but the program does not give encoder
errors. The program is executed with a 10 ms cyclic interrupt.
Here is my code:

Hi Rmp14,

there are more information needed to be able to help you. Maybe this topic will help you to provide detailed information, even if it is for the visualization conference: What do we need to solve your problem?

BR,

Noodles

Hello Rmp14,

please don't delete your posts, every post can be helpful for future users to get hints/ solutions if they have the same question :) So thank you for posting your solution, that's helpful! 
Can you maybe tell us which PLC and software you are using? 

BR,

Noodles

 Hi Rmp14,

Rmp14

(...) I wanted to close or delete this post, but I couldn't find such a button anywhere.

 you can only delete your posts, if no one has replied to your post yet.

Best regards,
Jen_Moderator

I am using step 7 v5.6. PLC VIPA 314-6CF02. 
I understand this forum for Siemens. But Vipa
programming is no different from Siemens. 
The difference is only in the hardware configuration 
and when accessing the counter.