PLC's are real time controllers whose function is to periodically read inputs, run several real time tasks, and control outputs, in a steady time period. PLC's are the standard platform for automation applications, and can they can be programmed in one or more of the 4 programming languages as defined by IEC116131-3; Instruction List, Ladder Diagram, Function Block Diagram, or Structured Text. PLC-EMU emulates this function: in a configurable time cycle, it will read the inputs from your card, run a task as programmed by the user, and send the appropriate outputs back to the card. PLC-EMU stands for Programmable Logic Controller EMUlator, this means that PLC-EMU is a tool for emulating PLC's on a Linux box, using I/O cards. This way you can build a cheap alternative to PLC's, for use with automation applications; it consists of a text-based Ladder Diagram parser, a minimal C API and an optional ncurses-based interface for online control. You need to install one or more PCI/ISA digital I/O card (analog I/O not supported yet.); it works in two modes: through comedi, and in user space. In Comedi mode, all you need to do is install and set up the apropriate Comedi driver for your card, and copy the setup values to PLC-EMU's config file. For more informations, and download, click here.