I have just pushed a commit through to Bitbucket for this project which implements function block operations for the IEC 61131-3 virtual machine. While still undergoing testing and further development, the implementation of this functionality addresses a major omission of functionality within the IEC 61131-3 virtual machine to date.
Surprisingly, the major effort associated with this functionality was associated with the implementation of the C library interface, allowing for function blocks to be written in both IEC 61131-3 languages and C, rather than the implementation of function block operations per se. To date, only the edge detection function blocks (F_TRIG and R_TRIG) have been implemented in the external C library for execution by the IEC 61131-3 virtual machine run-time, but next immediate task will be to extend this implementation to cover all standard function blocks defined within the IEC 61131-3 standard such that these are all immediately available, in the most optimised manner, from within the run-time environment.
Nevertheless, the rudiments of this functionality is now in place and available to be pulled from the git repository on Bitbucket.