frame_subnumber( <variable> )


This sets 'variable' to the subframe page number of the current page, in p###.# form, a number between 0 and 15.

On entry, 'variable' should be 16 to have the page number returned in hex.


If a page has no subframes, then this may validly return 0.

Technically, this returns the value of the Minutes-Units byte (which is a four-bit value); thus pages with more than 15 subframes will be reported incorrectly; however it is rare to have a page with so many subframes.
If you require handling for larger values, please get in touch with me.