Converting modicon to AB

bwest

Member
Join Date
Jul 2003
Posts
1
I have been given the tedious task of converting an old 484 Modicon program to a new AB SLC5/03, and have never touch a Modicon before. Is there any programs for converting the programs? or do I just do it line by line. And are they any pit falls I should watch out for?

Regards
 
I'm not aware of any utility to convert from Modicon 484 to SLC. You'll just have to tough it out.

There are pitfalls to watch out for. Modicons of that vintage have an unusual method of solving ladder logic. Each network is solved by evaluating each cell from top-to-bottom and left-to-right. If the original programmer put multiple rungs in a network, then you need to consider whether it was done simply to save memory, or whether the intent was to take advantage of that scan strategy.
 
One trick I've used when converting from other PLCs to AB is to use SYMBOLS in the AB that matches (as close as possible) an address in the existing program.

For example, You may wish to create a data file N40:0-249 which corresponds to Modicon register 40000-40249, N41:0-250 is 40250-40500, and so on.

If you assign those addresses with the symbol of, for example, N40:0 = A40000, N40:1=A40001 and so on, then when you come to an instruction that uses the address, just type in the symbol instead of the address. RSLogix will substitute the N40 address for the symbol name, and you won't have to be looking up each address as you re-enter the code.

The example above doesn't show how handy that can be, since N40:001 is pretty clearly 40001, but when a you get a timer in the middle of the 4xxxx's, it's nice to know that T4:15.PRE corresponds to 40117, and all you need to do is type in 'A40117' in the MOV block that is setting the preset, and you'll get the T4.PRE, not N40:117. See?

If you can export your address descriptions from Modsoft/Taylor/whatever, and massage them in Excel to create a CSV for AB to import, this can speed up the process considerably, and save you from typos.
 
I have just completed a task of writing a script to convert 484 Taylor logic to Modicon Modsoft.. to use the logic for Quantum..

I had to decode the file structure of both the package.. parse one and then produce the other.

If you need any information about 484 file structure mail me at

[email protected]
 
If the old program used sequencers, it'll get interesting. It's been awhile but, it seems like Modicon's sequencers were a sort of weird one-of-n decoder type of thing.
 
I did few conversions from Modicon to AB and I found, that it is really easy to do with Control Logix PLC no in SLC.
In CLX you can create all data datbles with same names as address in Modicon program.
The only problem I see that Modicon allows some ladder structures impossible convert directly like this:

--[ ]----------+--[ ]--+--( )--
| |
--[ ]--+--[ ]--+ |
| |
+--[ ]----------+

 

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