What it does in the rack
The Siemens 6GK7543-6WX00-0XE0 is a PROFINET communication processor for the ET 200SP distributed I/O family. It puts a 10/100 Mbit/s interface into the system with DCP, NTP (including secure NTP), and LLDP support out of the box. Two of these CPs can plug into one CPU, and you can run BA Send and CM DP simultaneously alongside it. Supply voltage is 19.2 to 28.8 V DC, pulling 6 W. That's the only power rail it needs — no additional auxiliary feed required. STEP 7 Professional V14 (TIA Portal) or higher is needed to configure it.
Mounting and slot limits
On the security side: stateful inspection firewall, blocking of communication via physical ports, and IPsec VPN (with SINEMA RC support). Encryption goes up to AES-256; hashing uses MD5 or SHA-1. It also supports SNMP v1 and v3, MIB, and SICLOCK time sync. But it does not pass on time synchronization — each CP needs its own NTP feed.