Joe E.

What OS are you using? The PIC will only work on Windows XP Service Pack 2 and earlier. SP3 and newer broke the serial port driver. You also need a native, built-in COM port. No virtual COM ports (USB, etc.).

It's been a while since I worked with a DH+ HMI (or even PanelBuilder 32 for that matter...), but if you can see it in RSLinx, you should be able to download to it. And if you have access to the DH+ network, you should be able to see it in RSLinx. You said you have the round port AB cable...is that the 1784-U2DHP module? It's a USB to DH+ converter. If so, it can plug into the round Mini-DIN DH+ port on the SLC 5/04 (as pturmel said, the 5/03 has DH485 with an RJ45 connector, only the 5/04 had DH+) without disrupting the DH+ network at all, as long as  you don't introduce an address conflict. On the 5/04, the round mini-DIN and the 3-pin phoenix-style connector are just different hardware connections to the same DH+ port. If you have a cable that has the mini-DIN on one end and a 9-pin d-sub connector on the other, that won't work. What you have is almost certainly a serial cable designed to talk to MicroLogix PLCs. If you don't have a 1784-U2DHP,  you'll need some other hardware to get to the DH+ network. If you happen to have the right ControlLogix hardware laying around collecting dust, you can assemble a chassis, power supply, Ethernet module, and a 1756-DHRIO module. That will definitely work as a pass-through for RSLinx to see the DH+ devices. Or, you can use a ProSoft gateway. If I didn't have any of that on hand already, I would probably try one of these before either of those: https://www.plccable.com/allen-bradley-1784-u2dhp-alternative-usb-to-data-highway-plus-dh-anc-120e/ (No specific endorsement for that, but everything else I've bought from them has worked beautifully). Incidentally, that note on page 202 of the manual refers to reaching an RS232/DH485 HMI via passing through the DH+ port on a SLC 5/04. In other words, you connect your PC to the DH+ network and pass through the SLC to get to the RS232/DH485 HMI. If you look at page 189, it says you can use the DH+ port to (among other things) transfer applications over the DH+ link from a computer with a DH+ connection. It doesn't say anything about getting to the HMI's DH+ connection via the RS232 port of the SLC, but it might work. It's worth a try, at least, if you have access to the 5/04's RS232 port.

I can't help you with your question, but you'll probably get more attention in the Mitsubishi sub-forum.

I agree. Make it a lot bigger than you need. You can edit code online but you can't add/remove LAD files or add/resize data files without a download.

The user manual says it's a no load or short circuit condition. Or, if it's a /B module, a field power loss. I think it's really weird to flash red on a no load condition...especially for unused output points. That seems strange to me...

In general, I prefer to use MSG Read instructions. That way the destination registers show up being written in the program cross-reference. I think I remember seeing somewhere that reads take slightly lower resources as well, but I could be mis-remembering that. I wouldn't think that the data traffic would be too much, but it all depends on how much data is flowing back and forth and how often the MSG instructions are executing. I like having things simple and easy to understand, and I think having a read MSG straight from the source PLC is simpler. There's also less to go wrong, like if PLC C is shut down for some reason PLC B would lose the data from PLC A. About the only time I deviated from using read instructions is when I went between a PLC5 and a CompactLogix. I found the routing and MSG path to be far easier to manage in the Logix 5000 PLC than in the PLC5, especially since it was hopping from DH+ to Ethernet via a ControlLogix backplane. In that case, I made sure to scrupulously document it and put info in the destination register's description as to its source. I know, that violates "simple and easy to understand", but I didn't have a lot of options at the time. We had about zero budget and the PLC 5 didn't have Ethernet. We had the ControlLogix hardware sitting around so it was cheap to install.

I pulled up an OLD project from a PLC5. The Tag/Expression I used was: {::[PLC540B]N19:3}/10, with the curly braces. That was directly in the object properties connections tab, not in the tag database. I would try putting the address directly in the object on the display to see if it works.

Back when I was supporting the S7-300s, there was a signal module for the S7-300 that added an Ethernet port. There were actually 2 models: the cheaper one worked only for getting online with your PC while the more expensive one supported adding I/O. I would suggest the more expensive one that supports I/O because we found that adding a ProSoft gateway module later would work with the better one but not the cheaper one. Another option is this: https://www.ibhsoftec.com/IBH-Link-S7-PP-Eng It attaches to the MPI port and provides an Ethernet connection. As i recall, they were a bit of a pain to get working at first, but worked great once properly configured. They were only for getting online with a PC (no I/O control) and added a driver to your PG/PC interface, which is where the pain came in. If you're looking for remote access to the PLC via another PLC or SCADA system, I think you'll need the in-chassis signal module. Another option is to upgrade the CPU to a 2PN/DP model that has an on board Profinet port. I believe that all of these options are going to involve the aftermarket, though. I'm pretty sure the S7-300 platform is obsolete, but I could be wrong. I've been away from that world for a bit over 3 years now. I have a procedure somewhere that I came up with when doing that upgrade. It was a little clunky but it worked.

  When I started at my last location, that's what they did! They had spare parts laying around so they put together a chassis, power supply, ENBT, and DHRIO on a cart with a UPS for the desktop PC. They also had a data switch to select between the 9-pin RS232, 25-pin RS232, PLC-2 cable, and SLC 150 cable. It was an impressive setup, with 2 carts set up that way. With the UPS batteries never lasting, and the leased PCs having to go back to IT, we got laptops and the -U2DHP adapters. When the U2DHPs started failing, we got the ProSoft modules. At my current location, we don't have any 5/04s (that I've found so far...) and no DH+ at all, so it hasn't been an issue.

On the SLC 5/04, the 3-pin Phoenix connector and the round mini-DIN are both the DH+ channel. That means you'll need a DH+ adapter for your PC. The AB 1784-U2DHP adapter is very expensive and very fragile. And not repairable. I've seen them last a while or fail quickly. They just stop working. They'll power up, LEDs turn on, but RSLinx doesn't see any DH+ devices behind it. The failure is sudden and complete (it doesn't get flaky and then quit, it just works one day and doesn't the next). I've used a Prosoft EtherNet/IP to DH+ gateway module very successfully. Biggest downside (besides cost) is that it needs an external power supply. If I need to do it again, I'll probably try this: https://www.plccable.com/allen-bradley-1784-u2dhp-alternative-usb-to-data-highway-plus-dh-anc-120e/  

Ditto what Bob said and also verify your driver settings. The red "X" means RSLinx can't see it. The yellow question mark means RSLinx doesn't recognize it. Devices it's never connected to will always show both until the first time it connects, then it'll show the red "X" on top of the device's icon. Also...this seems weird....try a different network cable. I've seen almost that exact thing happen where I could ping but not connect. Jumped through all the hoops that could be jumped through and finally, after a couple of hours, swapped the cable and it just started working.

I finally got back to my desk where I have access to a spare CompactLogix. In V19, I created a new project. When you go to Communications -> Who Active, browse to the PLC and highlight it, and click "Go Online", what happens?

That's really weird....when you browse to it in RS Who from within RSLogix, does it show up?

I'm not 100% sure, but the "Set Path" may only be available while online. Try going to "Communications" -> "Who Active", and then browse to the PLC.

It's been a few years since I did much with ControlLogix (we're mostly CompactLogix and SLC500 here) and I don't have a test rig to confirm, but I'm 99% sure you can plug in the -EN2T, add it to the IO tree, and set up MSG instructions without disrupting operations.