Explicit exchanges are exchanges performed at the user program's request, and using the READ_STS instructions (read of status words).
These exchanges apply to a set of %MW objects of the same type (status) belonging to a channel.
NOTE: These objects provide information about the module (e.g.: type of fault on a channel).
General Principle for Using Explicit Instructions
The diagram below shows the different types of explicit exchanges that can be made between the processor and module.
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 do this, two types of information are available:
The following diagram describes the management principle for an exchange
NOTE: In order to avoid several simultaneous explicit exchanges on 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.
