LC3-PCI , Loop Controller, 3-Channel, plastic fibre optics
The Loop Controller is the computer’s access point into a control system implemented with Group3 Control hardware. Three software interfaces have already been developed by Group3 for customers to use with their applications: for WonderWare InTouch (via a DDE server), LabVIEW and C++.
The Loop Controller card fits into a computer and is an integral part of the Group3 Control product range. On each Loop Controller (LC) card can be one or more Loop Controllers, each with their own processor, dualport RAM and fiber optic connectors. The Loop Controller processor handles all communications with the remote hardware, which can be a loop of Group3 Device Interfaces (DIs), a loop of Group3 Teslameters (DTMs), another Loop Controller or any other devices that can communicate serially. Therefore the computer is not directly involved in the communication. With the exception of DIs operating back to back (DI to DI mode) all Group3 Control applications require the use of a Loop Controller.
Each Loop Controller has a block of dualport RAM (shared memory) on board. The dualport RAM is shared between the Loop Controller processor and the application program running on the computer. The computer and the Loop Controller processor exchange data through this
memory. In fact the only access the computer has to the Loop Controller is via the this dualport RAM. For example, to send a new output (control) value to an I/O board in a DI, the computer simply writes the new value into the appropriate area of the dualport RAM. The processor on the
LC card automatically uplifts this new value and sends it out on the fiber optic loop to the DI. The Loop Controller also continually interrogates the DIs on its loop and updates the dualport RAM with the new input (status) values. The computer just has to read the dualport RAM to get the latest input values read back from a DI.