Hello Walter,
If the APC2100 isn’t staying on long enough to obtain the logger via online connection, I’d recommend that you use the CF / CFast card method of the linked Service Mode guide to look at the logger. You will need a CFast card reader for this.
Service Mode - What is it and how to collect diagnostics - Share Info & Ideas - B&R Community
To address the direct question:
The APC2100 doesn’t have an RS232 port as a programming interface. If there is an RS232 interface card (ex. 5ACCIF01.FPLS-000), then you could theoretically connect using the RS232 interface using serial INA. You would face the same issue of reboots that you saw with an Ethernet connection, and it would be much slower.
Best regards,
Austin