S7-200 CPU with precise supply tolerance and retentive backup
The Siemens 6AG1214-1AD23-2XB0 is a current-production CPU from the S7-200 family, designed for small to medium automation tasks. It requires a 24 V DC supply with a permissible range of 15.4 to 28.8 V, so a regulated supply within those limits is expected for reliable operation. Power dissipation is 7 W typical — within the range of a passively cooled panel, but check local ambient temperature if stacking near other heat sources. Retentive data is maintained via a high-performance capacitor for at least 70 h at 40 °C (100 h max), with an optional battery module extending backup to 200 days. For critical processes where power loss retention matters, factor in the capacitor’s temperature dependency.
Input characteristics and high-speed counters
Digital inputs are configurable as sink or source per group, which adds flexibility when mixing sensor types. Signal thresholds: "0" at 0 to 5 V, "1" at minimum 15 V — consistent with standard 24 V logic families. Six independent high-speed counters (30 kHz each, 32-bit) can be used as up/down counters or quadrature encoder inputs (up to 20 kHz in A/B mode). Each counter has parameterizable enable and reset, plus interrupt capability when setpoint is reached. Input filtering is adjustable: minimum 0.2 ms, maximum 12.8 ms for a "0" to "1" transition. Tune filter time per input to balance noise immunity vs reaction speed.
Integrated communication: MPI and PPI
An integrated RS485 interface supports MPI slave mode for data exchange with MPI masters and PPI protocol for programming, HMI, and CPU-to-CPU communication. Transmission rates are selectable: 9.6, 19.2, or 187.5 kbit/s. Shielded cable max. length 500 m, unshielded 150 m. For noisy environments, shielded cable at 187.5 kbit/s is recommended to maintain signal integrity.
Programming languages and memory architecture
Supports LAD, FBD, and STL programming, allowing reuse of existing logic regardless of programmer preference. The instruction set includes bit logic, timers, counters, integer and floating-point math, conversion, and communications instructions. Program and DB1 data are stored on integral EEPROM (no battery needed for program retention). Retentive memory bits, timers, and counters use a high-performance capacitor for buffering; the optional battery extends backup for long-term power-loss retention. Cycle time is free-running in OB1, with interrupt and time-controlled execution (1 to 255 ms). The 256 timer capacity covers typical logic sequences without overflow.