Fail-safe CPU for ET 200S with 192 kB
The Siemens 6ES7151-7FA21-0AB0 is an IM151-7 F-CPU — a fail-safe CPU module for the ET 200S distributed I/O system. It integrates 192 kbyte of work memory and handles 244 byte each of process input and output data, making it the brains of a safety-oriented remote rack. This CPU communicates over Profibus DP with DPV1 extensions, using an isolated RS 485 interface. It supports routing, alarms, and forcing, and can serve as a Profibus DP slave but not as a client.
Programming languages and memory backup
Programmable in LAD, FBD, STL, and optionally SCL, CFC, GRAPH, and HiGraph. The CPU retains program data and retentive variables across power cycles, but must be restarted after each restart. Backup time is 6 weeks at 40 °C ambient. The retentive memory covers inputs, outputs, memory bits, data blocks, timers, and counters. The I2t rating is 0.09 A²·s — relevant for sizing the power supply and protecting the module's internal electronics against short-circuit energy.
The module is not expandable and does not support MPI or TCP/IP. Its width is 60 mm for the CPU body, with the DP master interface adding 35 mm. Height is 119.5 mm, depth 75 mm — fits standard ET 200S rail spacing.