What this CPU brings to a rack
The Siemens 6ES7412-2XG00-0AB0 is an S7-400 CPU with 244 byte inputs and 244 byte outputs, 64 kB work memory, and a 1 ms resolution timer. It supports MPI, RS 485, and STEP 7 programming in LAD, FBD, STL, SCL, GRAPH, HiGraph, and CFC. The CPU handles up to 16 overall connections (one reserved for PG/OP), with 10 via CP and 16 via CP LAN or PtP. Forcing, routing, and SYNC/FREEZE are built in. The FM function block capacity is 16, limited by slots and connections.
Memory and retentivity
Work memory maxes at 64 kbyte. The preset retentivity is none — no retentivity by default. Adjustable retentivity is available if the application needs it. The CPU is not expandable, so the 64 kB is the ceiling.
Communication and connectivity
Two integrated interfaces: MPI and RS 485. MPI supports routing. RS 485 is isolated. The CPU can act as both client and server. For PtP and LAN connections, use a CP — up to 16 each, limited by slots. Via IM 467 you get 4 additional connections. The overall connection limit is 16, one reserved for PG/OP.