Is it possible to connect to an M340 PLC with an embedded Ethernet port via a default IP address?

Yes. Every M340 with an embedded Ethernet port has a default IP address derived from its MAC address, giving you a way in even if no IP has been configured yet.

How it's derived:
The default IP address takes the form 84.a.b.c, where a.b.c are the last three octets of the MAC address, converted from hex to decimal.

Example: MAC address is 00.80.F4.02.EA.6A

• 02 Hex = 02 Decimal
• EA Hex = 234 Decimal
• 6A Hex = 106 Decimal

Default IP address will be 84.2.234.106