We have a 2, NCU573.5's that are not communicating with the PCU50.3 + operator panel.   
Alarm #120202 exists after starting up.  

Connection to the PCU50.3 + operator panel is via the NCU's MPI-X101.  There are no drives connected to this system.

Settings on the START-UP \ HMI \ OPERATOR PANEL screen are…

Connection -  1:1
Bus -   OPI (1.5 Mbaud)
HMI address -  1
NCK address - 13
PLC address - 13

NC/PLC memory is cleared by

1. Set S3=1,  S4=3 
2. Apply power to NCU
3. Wait for 7-segment LED = 6
4. S4 = 2, 3, 2
5. Wait for red PS LED to be steady
6. S4 = 0

Alarm #120202 is then displayed with no other active alarms.

Shouldn't there ALWAYS be communication between HMI and NC with the above settings?

The same alarm also occurs when a 2nd NCU573.5 is connected to the same PCU50.3 + operator panel with the same connection/cables and the same steps are followed for clearing NC/PLC memory.

We then move connections to a NCU573.4.  Following same steps, we get NC/HMI communications after cycling power.  No #120202 alarm and amber CB LED flashing intermittently.

At no time during the startup of the 2 NCU573.5s does the CB LED flash.

I will also mention that these NCU573.5s were working at one time.  They stopped working sometime after connecting them together via X101 connection for testing of a 2 NCU system connected to the single HMI + operator panel in a m:n configuration.  Settings on the HMI \ OPERATOR PANEL screen were changed many times with attempts to get communications working again.  

Do we coincidentally have 2 bad NCU573.5s?   Is it possible there is an HMI address setting that is not getting reset after clearing NC/PLC memory?

Screenshots of all MMC.INI and NETNAME.INI files that exist in the oem and user folders are attached.  Neither of these files exist in add_on folder.  Also attached is NETNAMES.INI file from the mmc2 folder.  I have tried changing "bus=btss" to “bus=opi” and reboot HMI but still no communication.
 

Thank you for looking into this.

Attached are the photos you requested.

Sorry. I forgot to include the most important detail... both POK and PR LEDs are steady green. All other LEDs are off. At no time do I see the CB LED flash amber.

Yes, I do have Step7 Simatic Manager software.

The PCMCIA card has been reloaded with NCU software (v07.04.32).

History of NCUs

Our system is strictly for machine simulation purposes. These components are not being used on machines. There are no drives or I/O connected to our system.

Both NCU573.5’s were communicating recently (~3 weeks ago) when individually connected to the PCU50.3 in 1:1 (1 PCU + 1 NCU) configuration.

When each NCU was communicating to the PCU50, they did have low battery alarms. The batteries have since been replaced.  Voltage is 2.9 volts but is enough when it is used with our NCU573.4 that is communicating.

When NCUs were connected together via the X101 connection for testing of an m:n configuration (1 PCU + 2 NCUs) is when communication problems appeared.

At one point both NCUs X172 connections were also connected together and to the same U/E (I/R) module X351 connection for power source purposes. Could this have introduced problems in the NCUs?

Also, at some point, we noticed one of pins one of the NCU’s X172 drive bus connector was bent such that it was not making contact with the ribbon cable connector. The second NCU may have been connected to the first NCU via the X101 connection at the time, however, I do not expect this to be source of our problem because pin was bent such that it was not shorting with the other pins.

Bent pin is now corrected, changed back to 1:1 (1 PCU + 1 NCU) connection, restored original mmc.ini, deleted …oem\netnames.ini file, but cannot regain communication with either NCU. 

I think MPI cable is OK.  If I move it from NCU573.5 to NCU573.4, I get NC/PLC communication with 573.4 but not 573.5.

I am not 100% sure of your instruction “Make PC/ PG setting to 1.5G baud rate”.  I assume you mean 1.5M baud rate. After doing this, I do not display any accessible nodes.

Please confirm the steps I have taken to make this setting, as shown in “PCsettingTo1_5Mbaud” attachment, are correct.