CPU 317-2DP for the S7-300 rack
The Siemens 6ES7317-2AJ10-0AB0 is a CPU 317-2DP for the S7-300 rack, handling 244 byte of process inputs and 244 byte of outputs — enough for a medium-sized kiln or mill control block without an expansion rack. It runs LAD, FBD, STL, SCL, GRAPH, and CFC, plus HiGraph for state-machine sequencing.
Fieldbus and programming toolchain
The integrated PROFIBUS DP interface runs at up to 12 Mbaud and supports routing when the interface is active. It can act as DP master (class 1) or as a DP slave via a loadable FB. The latest GSD file is published at the Siemens PROFIBUS GSD portal. Programming requires STEP 7 V5.2 SP1 or higher with the appropriate hardware update package. The CPU does not support MPI or PROFIsafe.
Memory, retentivity, and expansion limits
Work memory is 4 096 bytes maximum. The CPU has no retentivity preset — retentive data must be explicitly configured and restarted at each restart. Forcing is supported on inputs, outputs, memory bits, DBs, timers, and counters. The CPU is not expandable and not adjustable. It supports up to 4 CPs on the LAN and up to 8 CPs for PtP connections. The FM 8 rating means it can handle 8 function modules in the rack.
Mechanical fit and isolation
The module is 80 mm wide, 125 mm high, and 130 mm deep — it occupies two standard S7-300 slot positions. The backplane bus is isolated, so the CPU can sit next to a power supply or an SM without ground-loop coupling through the rack.