Greetings to all,
from Ken Moore:
As Ron mentioned the only obvious gotcha is the I/O addressing, one slot, two slot, 1/2 slot etc...
no offense taken or intended, Ken ... but just to be absolutely correct, I said that the addressing modes are ONE big gotcha ... but I also reiterated that the Block Transfers (particularly for analog signals) which had already been mentioned by other responders were another issue ...
so to nail it all down, in my opinion the biggest issues would be:
(1) the PLC-5 uses Block Transfers to handle analog signals ... and the PLC-5's analog signals will addressed to the integer files (example: N7:54) NOT to the Input Image table (example: I:7.0) like the SLC's analog signals ...
(2) the PLC-5 uses two-slot, one-slot, or half-slot addressing modes for its I/O signals ... the SLC only uses these (rarely) for certain remote I/O configurations ...
so in the "what are the differences?" department, those two are the "biggies" ... once you've got those nailed down, you can probably muddle your way through anything else that comes along ...
worse case scenario: a guy who says he "knows all about Allen-Bradley" gets himself hired as a maintenance technician for a new job ... his first work order on the first day of the new job involves a 4 to 20mA analog input signal on a PLC-5 system ... unfortunately for our hero, the Allen-Bradley platform that he "knows all about" turns out to be the SLC-500 platform ... based on his existing knowledge, he's expecting to see an analog signal with an address something like I:7.0 with a data range from 3277 to 16384 ... this is the format that he's familiar with ... this address would indicate that the input lands on the Input Image table and corresponds to an analog input module physically located in slot number 7 of the chassis ... and further, to the first channel (word number 0) from that analog module ... oops! ... the PLC-5 doesn’t work like that ... instead this rung is just one of the pieces of the puzzle ...
[attachment]
now the steps required to find and then decipher this rung ... and then to track down the “problem” signal to an address like N7:54 (and a default data range of 0 to 4095) are NOT the type of things that someone totally unfamiliar with Block Transfers and the way that the PLC-5 handles its analog signals is going to be able to quickly figure out ... especially while the new boss is breathing down his neck and wanting to know when the machine is going to start making money again ...
this situation is not a pretty picture ... but I have seen it happen ...
so in the final analysis, the RSLogix5 and RSLogix500 software packages are certainly more “alike” than they are “different” ... and the PLC-5 and the SLC-500 hardware platforms are certainly more “alike” than they are “different” ... but still ... there ARE some substantial differences that should not be considered “trivial” when trying to cross over from one platform to the other ...