HMI TP170A and S7 300

I want to indicate to the machine operator via the HMI if the communications has been lost to the PLC or if the PLC has faulted and gone into stop mode. I've enabled the system mesages on the HMI so if the communications are lost i.e disconnect the MPI cable the system message is displayed for the maximum time of 255 seconds. But the machine operator my not be at the machine in that time so may miss the message. Is there a way to latch thease messages.
Also if the PLC faults and stops the hmi does'nt report this type of fault at all. Is there any other ways of reporting thease type of faults.

not sure about S7, but AB has a bit (S:1/7, IIRC) that is used for comms active. Check your S7 documentation for something like this, and tie it in to an HMI bit that will go true if not active. As far as latching, check the documentation of the HMI (there again, not familliar with the HMI type).