Explicit exchanges are exchanges performed at the user program's request, using the following instructions:
These exchanges apply to a set of %MW objects of the same type (status, commands or parameters) belonging to a channel.
NOTE: These objects provide information about the processor or the module, can be used to command them (e.g.: switch command) and to define their operating modes (save and restore adjustment parameters in application).
NOTE: The READ_STS and WRITE_CMD instructions are executed at the same time as the task that calls them and always correctly. The result of these instructions is available immediately after their execution.
General Principle for Using Explicit Instructions
The diagram below shows the different types of explicit exchanges that can be made between the processor and the communication channel:
During an explicit exchange, it is necessary to check its performance in order that data is only taken into account when the exchange has been correctly executed.
To this end, two types of information are available:
The following diagram illustrates the management principle for an exchange:
NOTE: In order to avoid several simultaneous explicit exchanges for the same channel, it is necessary to test the value of the word EXCH_STS (%MWr.m.c.0) of the IODDT associated to the channel before to call any EF using this channel.
