From OpenSCADAWiki
In OpenSCADA this mechanism is implemented by the following modules of the subsystem "DAQ":
- JavaLikeCalc — calculator on the Java-like high level language. As a data source, a user program in a Java-like language acts. Parameter attributes of the module synchronously address the inputs/outputs of the computing context of the user function.
- LogicLev — module of the logical-level parameters of the data acquisition, see more about it in section 3. As the data source of this module stand other parameters of the subsystem "Data acquisition" and the execution context of the parameters template. parameter attributes of the module synchronously address the attributes of other parameters in the reflection mode of the parameters of the subsystem "Data acquisition", or the inputs/outputs of the execution context of the template when work under the template.
- BlockCalc — calculator in the language of block diagrams. As a data source, the user block diagram is stood. Parameter attributes of the module synchronously address the inputs/outputs of the blocks of block scheme.
- DAQGate — module of the reflection of the controller objects of the remote OpenSCADA-stations on the local one. In the module the synchronous mode for recording data is implemented.
- ModBus — module of the accessing to the sources data through the ModBus protocols family. In the module the synchronous mode for recording data is implemented.
- DiamondBoards — module of the data accessing of the PC/104 cards of the Diamond Systems company. PC/104 boards are available on the ISA-bus, hence are local and available relatively quickly. When data acquisition is made not by interruption the access to the values of the ADC is synchronous. Recording mode of the DAC values always works synchronously.