There's also some stuff on the specs about a temperature probe, but it's not clear if that's onboard or if it's configurable to a thermocouple/RTD connection.
Most likely the internal chip temperature sensor? Seems a very big stretch to call it that, but it's not uncommon as a publicity stunt. I'd be interested to see if they even bothered fitting the 32678Hz crystal to the internal timer of the board to get the RTC functionality.
So you are saying there is no online programming with openPLC ?
I don't know, I'm just thinking what may be possible.
I've browsed through the openPLC website every now and then and have seen a large increase in the development of it. Originally it was aimed at programming a normal Arduino (32KB program memory running at 16MHz) with IEC languages, so all it did was translate the IEC language to C/ASM and then compiled it and downloaded. As you can imagine, with a chip that small online programming was not possible.
It's since developed much more where the software is actually aimed at raspberry pi and the smaller style arduinos are considered for IO. So there's definitely possibility for online change.
Bear in mind that openPLC is or was a personal project. Arduino may use it or parts of it, or they may well get someone to develop it for them...
The chip they're using is powerful and should have enough memory to allow online mods, but it would mean that they have to create the OS to run on the chip and accept compiled blocks to be run. I don't doubt of the Arduino team's capabilities, but doubt that they'll implement it. I may well be very wrong though.
I am thinking and does the LOGO allow online changes?
EDIT:
Just thought that STM32 has a vested interest in this so they may well develop some of the functionality and hand it over to Arduino.