IOASYNC – Asynchronous reading and writing

Block SymbolLicensing group: STANDARD

Function Description
The IOASYNC block is designed for asynchronous reading and writing of inputs and outputs. Unlike the INSTD, OUTSTD, INOCT, OUTOCT blocks and their variants, the operation of the IOASYNC block is not controlled by the periodic timing of the driver. The main difference is that reading and writing occur exclusively at the moment of detecting a rising edge off$\to$on signal on the respective inputs. Writing the value from the input u is triggered by a rising edge on the input WF, while reading to the output y is triggered by a rising edge on the input RF.

Unlike other blocks, where writing can be canceled by setting a special signal _WriteEnable to off (see documentation for the respective driver), the IOASYNC block ensures that at the startup of the executive, not even a one-time initialization of the value to be written occurs. This initialization may be undesirable in some applications.

To establish a connection with a specific driver signal, it is necessary to rename the block instance according to the established format of driver signal names, which uses a pair of underscores, similarly to the INSTD block.

This block propagates the signal quality. More information can be found in the 1.4 section.

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