Hi Roy.
These things allways happens 5 minutes to twelve so to speak.
I have seen something about the S7 CPUs storing the X1 interface settings in onboard flash (not the MMC flash). For some reason that should make the CPU reachable with the settings chosen by the programmer even if the main program is lost. It should apply to S7-400, but I am not sure if it also applies to S7-300.
This could mean that you cannot reset the X1 port without an online connection (catch-22).
But as I said, I am not sure if it applies to S7-300.
I am afraid that the default for the X2 interface is that it is NOT networked, so if the CPU has been reset, then it can have shut down the X2 port
Try the diagnostics function with the Set PG/PC interface utility.
It can help you to establish the CPU ports settings.
Try various baud rates and modes.
edit: Try to change the node address of the PC. It is possible that you have set the S7 to the same address as the PC.
Try both X1 and X2 interfaces.
Try another online adapter or another PC.
If you have a MMC prommer, then try to write a simple program where both X1 and X2 ports are set to known parameters. Then use the MMC to load the program in the CPU.
Good luck.
edit:
fred, MPI has exactly the same electrical properties as Profibus. The dogma "MPI=187.5 kBaud" comes from the beginning when S7 was launched. Then all MPI ports where max 187.5. It still applies to all ports that are only "MPI" rated, in contrast with ports that are "MPI/DP" rated. The MPI ports in the smaller S7-300's are "MPI" ports without electrical isolation, ad max 187.5k. The ports in Roy's S7 317-2DP are "MPI/DP" and "DP", both with electrical isolation and max 12M.