From, INSTD – Signal connection or input
Block SymbolsLicensing group: STANDARD
Function Description
The two blocks From (signal connection) and INSTD (standard input) share the same symbol.
They are used for referring to another signal, either internal or external.
The From block can be used in both the REX control system and the Matlab-Simulink environment, the INSTD block exists only in the REX control system.
The following rules define how the RexComp compiler distinguishes between the two block types:
- If the parameter GotoTag contains the __ delimiter (two successive ’_’ characters), then the block is of the INSTD type. The part of the parameter (substring) before the delimiter (DRV in the example above) is considered to be the name of an IODRV type block contained in the main file of the project. The RexComp compiler returns an error when such block does not exist. If the driver exists in the project, the other part of the GotoTag parameter (following the delimiter, A in this case) is considered to be the name of a signal within the appropriate driver. This name is validated by the driver and in the case of success, an instance of the INSTD block is created. This instance collects real-time data from the driver and feeds the data into the control algorithm at each execution of the task it is included in.
- If there is no __ delimiter in the GotoTag parameter, the block is of type From. A matching Goto block with the same GotoTag parameter and required visibility given by the TagVisibility parameter (see the Goto block description) is searched. In case it is not found, the RexComp compiler issues a warning and deletes the From block. Otherwise an "invisible" connection is created between the corresponding blocks. The From block is removed also in this case and thus it is not contained in the resulting control system configuration.
There is no INSTD block in the Matlab-Simulink system, even the blocks whose GotoTag parameter contains the __ delimiter are considered to be of the From type. This property is suitable for simulation of both the control system and the controlled system. The model can be connected via From and Goto blocks, whose GotoTag parameters include the __ delimiter. Moreover it is possible to use one .mdl file for both simulation and real time control without any modifications if the controlled system model is "hidden" in a subsystem whose name starts with Simulation. The RexComp compiler ignores (omits) such subsystems. For further details see [2].
Output
value | Signal coming from I/O driver or Goto block. The type of output is determined by the type of the signal which is being referred by the GotoTag parameter. | unknown |
Parameter
GotoTag | Reference to a Goto block with the same GotoTag parameter, which should be connected with the From block or a reference to input signal of the REX control system driver, which should provide data through the block’s output. | string |
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