S5-115U Hidden programmed Blocks

Join Date
Aug 2018
Location
Sharjah
Posts
49
I have a S5-115U, 941B.... In OB1, I can see some block calls Like JU PB16, JU PB17 and so on.... But in the Directory I don't see these blocks at all...

Rather I can see only PB1, PB2.......PB15, FB0,FB1,FB238,FB239,FB44,........FB250,FB251,FB252,FB253&FB254....in the Directory listing....

Can anyone tell me How can I access these Hidden Blocks?
 
S5 Keeps an address list for blocks which contains a pointer to the actual memory location of the code to be executed; so for PB's the is an array of 256 entries. When PBxxx is called, the address for the code to be executed is retrieved from the address table and execution will continue there.

Could it be that someone has manually entered code via direct memory editing (as mentioned in the other thread linked to by Gary)?

Nick
 
I have a S5-115U, 941B.... In OB1, I can see some block calls Like JU PB16, JU PB17 and so on.... But in the Directory I don't see these blocks at all...

Rather I can see only PB1, PB2.......PB15, FB0,FB1,FB238,FB239,FB44,........FB250,FB251,FB252,FB253&FB254....in the Directory listing....

Can anyone tell me How can I access these Hidden Blocks?


Hi!
Do you mean the online directory in the CPU?




I think the 941 will run happily even if some PBs are lacking.


Kalle


Edit: A PB can only be hidden by manipulating its header to change it to/from a DB. That is highly unlikely in your case.



This is an extremely dirty trick, and was used to store programs on extended memory (bubble memory) on ancient S5-150S/A/K/U -models. I can remember it was used on larger SIBET systems back in the mid. 1980s.
 
Last edited:
Yes Directory in the PLC doesn't show these PBs, but they are called in OB1....
And these PBs are not 1 or 2...More than a dozen PBs are there like that...
 
Actually the interface PC connected with this S5 has failed and machine is unable.to run in Automode as All the Orders, COME FROM PC to PLC.
Now some of the PROGRAMMED I/Os (NOT Physical) in the PLC Program are probably generated in these missing PBs.....
I just wanted to know What these I/Os are meant for...Also I m surprised that How these PBs are missing in the directory.....
 
I have seen situations where only some program blocks (OB/FB/PB/DB) were stored on the EPROM module by the programmer, and the rest were in the RAM of the CPU. If you lost battery power, only the blocks on the EPROM would remain, and the rest would be gone.

If you are completely down and out with an EPROM/EEPROM installed, I would try uploading all the blocks in the CPU with STEP 5, and then do an overall reset of the CPU.
 

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