Explicit exchanges are performed when requested using these instructions:
These exchanges apply to a set of %MW objects of the same type (status, commands or parameters) that belong to a channel.
NOTE:
These objects can:
-
provide information about the module (for example, type of channel fault)
-
have command control of the module (for example, switch command)
-
define the module’s operating modes (save and restore adjustment parameters in the process of application)
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 performance to ensure 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 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.
