There is another example with less system CPU load:
A FirstRun //any bit in bit memory or data block
JC nIni //skip initialisation, if allready performed
CALL "TIME_TCK" // CALL SFC64
nIni: L Backup //Word
Total - 11 instructions, to execute, with no CALL's, except initialisation moment.
I used http://en.wikipedia.org/wiki/Multiply-with-carry