How can “contained parameters” be accessed?
External access to internal variables of function blocks is contrary to the principles of good software design. Nonetheless, to accommodate exceptional cases and previous practice, the READ and WRITE services and associated access paths to internal variables are defined for management function blocks. However, this practice may substantially degrade system performance, reliability, maintainability and safety. • Are extensible user-defined function blocks permitted? IEC 61499 follows the usage of IEC 61131-3 and does not define a mechanism for specification of extensible inputs and outputs of user-defined function blocks. The use of the ellipsis (…) and accompanying textual descriptions is considered adequate for the specification of extensible inputs and outputs of standard function blocks in IEC 61499. • Can alternative graphical representations be used? Software tools can use alternative graphical, textual or tabular representations, so long as accompanying documentation specifies
