CompactLogix L23E + 485: cable wiring?

I have an existing mixed-device 485 modbus network, onto which a CompactLogix L23E is to be added. The network is a 2-wire setup, but all the wiring diagrams I've found for the L23E have indicated the need for additional wires, strangely resembling RS-232.

I've seen dozens of mentions on the net that the serial port on the L23E is Modbus capable (via logic) and supports DH-485, but can't get to the How of this puzzle.

Evidently, the serial port does NOT support modbus/485 as claimed, and i have to purchase a little 485->rs232 adapter.

Your confusion is probably coming from the term "DH-485", which is not the same as "RS-485".

Data Highway 485 is an Allen-Bradley proprietary protocol that was used by the SLC-500 family of controllers starting in the late 1980s. Physically, the trunklines of DH485 used 2-wire differential serial signalling with an isolated common conductor, which conformed to the EIA's RS-485 standard.

The DH485 protocol can also be implemented on an EIA-232 serial port, and MicroLogix and SLC-5/0x controllers started doing this in about 1995. The ControlLogix and CompactLogix family controllers also implemented DH485 protocol on their RS-232 serial ports later.

All ControlLogix and CompactLogix serial ports are RS-232 only. Multiple protocols can be implemented on those ports; DF1 full and half duplex, ASCII, Modbus, and DH-485.

It is very common to connect an RS-232/RS485 isolator and converter to a ControlLogix or CompactLogix. The Allen-Bradley 1761-NET-AIC is my default, but I like the DIN-rail mounted ones from B&B Electronics a lot for non-AB connections.

A slightly-related note:

The MicroLogix 1100 and 1400 controllers have an isolated 2-wire RS-485 port implemented in the 8-pin Mini-DIN serial connector along with the normal RS-232 pins. These pins are usually connected using the 1763-NC01 cable that gives you screw terminations.

This RS-485 port can be used for any half-duplex connection that the controller supports, including Modbus RTU and DH-485.

This feature is specific to the MicroLogix 1100 and 1400 controllers. The other MicroLogix family controllers with this 8-pin port (1000, 1200, 1500) use those pins for +24V DC for peripheral power.

That helps explain it. We've got a lot of experience with the micrologix 1400, where we do use modbus at the rs-232 port. Jeez, it's confusing.

Anyways, I did happen to have a -AIC in the stockroom, so it wasn't a disaster. We do not, however, have a cable, so I'll have to work out what sort of wiring it'll require, still.