The data acquisition system for TJ-II will consist of a central computer, containing the data base of the device, and a set of independent systems (personal computers, embedded ones, workstations, minicomputers, PLCs, and microprocessor systems among others), controlling data collection, and automated diagnostics. Each autonomous system can be used to isolate and manage specific problems in the most efficient manner. These problems are related to data acquisition, hard (mu s-ms) real time requirements, soft (ms-s) real time requirements, remote control of diagnostics, etc. In the operation of TJ-II, the programming of systems will be carried out from the central computer. Coordination and synchronization will be performed-by linking systems to local area networks. Several Ethernet segments and FDDI rings will be used for these purposes. Programmable logic controller devices (PLCs) used for diagnostic low level control will be Linked among them through a fast serial link, the RS485 Profibus standard. One VME crate, running on the OS-9 real time operating system, will be assigned as a gateway, so as to connect the PLCs based systems with an Ethernet segment. (C) 1997 American Institute of Physics.