According to the
SLC-500 Instruction Set Reference, appendix D, indexed indirect is available.
Even the lowly 1100 has an index register but it's not programmer accessible. You can enter a rung like MOV 4 S:24 and it will be accepted but an error will be thrown when you attempt to download.
The fact that S:24 exists, and is documented as "Index Register" is not an indication that Indexed Addressing is, or is not, supported by a particular processor model.
The S data-table is just an Integer file that contains "System Values & Flags". If you look at the S data-table for a ML1400, and choose "Integer" display style (Radix), the last element is S:65 = "User RAM Size".
In "Integer" radix you will definitely see S:24, it has to exist, but in "Structured" radix, it is the programming software that provides the nicely formatted view. For the ML1400, you will not find S:24 on any of the tabbed displays, ergo - Indexed Addressing is not supported.
Furthermore, the documentation for S:24 simply exists so that the programming software didn't have to keep a separate database for each processor model. If you look at "Address/Symbol" in the Database, you will see documented "S" addresses going up to S:86 = "DH+ Active Nodes", which is clearly not applicable to the ML1400, and many other processors.
LOGIX500 is not a perfect world, but if it says in the Help that "Indexed Addressing" is only available on SLC 5/02 to 5/05 and ML1000, then it's not even worth trying it on any other model, it will almost certainly produce errors.
