VBL on an Apple //c

[PBlokland@compuserve.com (Pim Blokland)]

In one of my BASIC programs, I use the VBL signal (PEEK(49177) for timing
purposes. This works on //es and IIgses, but lately I found out that it
does not work on a //c.
Apparently, on a //c you cannot see the VBL signal directly, but you have
to let the computer do it for you.

So my question is: could someone show me a small machine language routine
that I cann call from BASIC and which waits for the start of the vertical
blanking? (Or the end for that matter) And I would really appreciate it if
you can assure me that it does actually do the job, for I don't have a //c
and can't test it here myself.

Thanks in advance!

Groetjes, Pim