CPU 226 — panel fit and I/O count
The Siemens 6ES7216-2BD22-0XB0 is a CPU 226 unit from the S7-200 family, a compact PLC with 24 integrated digital I/O points. It measures 196 mm wide by 80 mm high by 62 mm deep, fitting standard control-panel backplanes with DIN-rail mounting. The power supply accepts 100 V AC to 230 V AC or 24 V DC, with the AC range covering global line voltages without a transformer tap change. Typical power dissipation is 17 W.
I/O and high-speed counting
The 14 digital inputs are source/sink configurable per group, with a 15 V minimum threshold for signal "1". Six high-speed counters run at 30 kHz each, 32-bit including sign, usable as up/down counters or for two incremental encoders with 90° offset pulse trains at up to 20 kHz. The 10 digital outputs switch resistive loads up to 200 W on AC (30 W on DC), with a maximum transition time of 10 ms for both turn-on and turn-off.
Communication and programming
Two integrated RS-485 interfaces support PPI and MPI protocols. PPI handles program upload/download and HMI communication (TD 200, OP) at 9.6/19.2/187.5 kbit/s. MPI allows data exchange with S7-300/S7-400 CPUs, OPs, and TDs at 19.2/187.5 kbit/s. Programming is supported in LAD, FBD, and STL. The command set includes bit logic, timers, counters, integer and floating-point math, shift/rotate, and communications instructions.
Memory backup and retention
The entire program is stored maintenance-free on integral EEPROM. Data DB 1 is also EEPROM-backed; current values reside in RAM with retentive memory bits, timers, and counters maintained via a high-performance capacitor. Backup time is 190 h minimum (120 h at 40 °C), extendable to 200 days with an optional battery module.