SLC 500 Migration to Compactlogix

I have searched AB knowledge base and can not find the answer to my question, maybe I forgotten how to read. I have a project to change 4- SLC 500's over to Compactlogix to get them off DH+ and onto enet, I will replace the processor in each of the 4 racks with a 1747-AENTR and leave the I/O and wiring intact. I have a total of 35 I/O modules in the 4 racks. I have been having difficulty coming up with just which CompactLogix Processor I need to use, on AB knowledge base I seem to be getting conflicting information. Which Compactlogix processor will handle 35 I/O modules ?

Any suggestion are welcome.

Thanks

I am doing something very similar to what you are doing. I am replacing a single SLC 5/04 with a 1769-L18. It has a single SLC rack and 4 Flex IO racks.

Since you are going to be connecting to your remote racks via Ethernet, it is not the total number of modules that you need to be aware of but the number of Ethernet/IP connections. If you use the Ethernet/IP Capacity Tool from RA you can figure out how many connections you will use up. I just ran the program using your configuration and you will use up 4-5 connections. Just about any CompactLogix Processor will work based on the # of connections you need.

Memory is going to be the other big thing to keep in mind. The Tag Based addressing of the CLX uses up more memory that the old SLC addressing did. The conversion I am doing is not completed yet but I have used about 25% (140k) of the memory. The originally processor had 32K. Someone on the Forum said that it is approximately 100:1. I would say that is a good rule of thumb.

So I would look at all your programs and add up the memory you are using. Multiply by 100 and find the CLX processor that has at least that much memory.

Good Luck.

I think you may be confusing Local Modules with I/O connections.

Each Compact Logix is limited to how many modules it can have in it's local chassis. This means both modules that are directly connected to the PLC via the interlocking backplane plugs, and modules in a separate bank connected to the first bank using 1769-CRLx bus extension cables.

If, however, you have a bank of modules in another chassis, connected via an ethernet adaptor - whether they be 1769 Compact I/O, 1734 Point I/O, 1794 Flex I/O, 1747 SLC I/O, or any other I/O you can lay your hands on, this does not count toward the Local Module limit. These are not local modules, they are remote chassis.

So, if you have modules directly connected to your compact logix processor you will have to confirm your CPU supports the number of local modules you intend to have - but as for the remote modules, it just counts the connections to the rack. I can't remember off the top of my head what the figures are for maximum number of ethernet/IP connections each Compact Logix supports, but I'm confident there isn't one out there that supports less than 4.

edit: Bullzi types faster

http://literature.rockwellautomation.com/idc/groups/literature/documents/sg/1769-sg001_-en-p.pdf

Page 13

Thanks to all of you for your information, and I did confuse local I/O on the back-plain with the remote I/O. I see why I was confused now.
Thanks
Keep it Simple
You guys are alright despite what Bullzi says.

I say everyone on the site is alright!!