What this CPU is for
The Siemens 6AG1212-1HD30-4XB0 is a SIPLUS variant of the S7-1200 CPU, hardened for ambient temperatures from -40 °C to 70 °C. It runs on 24 V DC (permissible range 20.4 V to 28.8 V) and ships with 1 Mbyte of integrated program/data memory. Programs in LAD, FBD, and SCL; communicates via PROFINET as a server over Ethernet TCP/IP. No onboard MODBUS, PROFIBUS, or AS-Interface. The CPU is not expandable — it has no slot for signal modules. I/O capacity is fixed at 1 024 byte inputs and 1 024 byte outputs, plus 4 kbyte bit memory and 15 dynamic connections.
Rated range and cold startup
Supply hold-up: backup time for the real-time clock and data retention is 240 hours typical, enough to bridge a long weekend without power. The input signal thresholds are defined at 5 V DC at 1 mA for logic '0' and 15 V DC at 2.5 mA for logic '1' — that callout matters when mixing 24 V sensors with longer cable runs where voltage drop can border the '1' threshold. Operating temperature spans -40 °C to 70 °C; storage range is wider but the operating limit governs panel location. The IP20 enclosure requires installation inside a closed cabinet free of condensation. PROFINET interface autocrosses, so no crossover cable needed.