User guide

CLOCKWORKS
43
Frame lock
The Frame lock check box is only available when your
MOTU interface is locking to external SMPTE time code
(in any form — MTC or LTC). It is not available when your
MOTU interface is in Internal sync mode.
To understand the Frame lock option, you first need to
know that your MOTU interface continuously monitors
incoming time code to detect any possible discontinuity in
the frame times as they advance. If your MOTU interface
detects more than five frames in a row that are not
continuous with respect to previous frames received, then
it does one of two things, depending on whether the Frame
lock option is turned on (checked) or off (unchecked).
If the Frame lock option is turned on (checked), and your
MOTU interface detects more than five frames in a row
that are not continuous with respect to previous frames
received, then it will stop converting altogether.
If the Frame lock option is turned off (unchecked), and
your MOTU interface detects more than five frames in a
row that are not continuous with respect to previous
frames received, then it begins to perform a kind of
“pseudo jam sync”. In this mode, it continues to convert
an uninterrupted stream of continuous time code, while at
the same time clocking off of the incoming time code.
Even though the frames it is generating no longer match
the frames it is reading, it will continue to remain in sync
with the incoming time code.
In other words, when the Frame lock option is off, your
MOTU interface ignores discontinuous jumps in
incoming time code by continuing to clock itself off of the
incoming time code without stopping (or pausing). In
doing so, it continues to convert a continuous,
uninterrupted stream of frame times based on the time
code to which it first locked.
Turn on Frame lock when you want your MOTU
interface’s frame times to match incoming frame times,
and you want it to stop converting altogether if there are
jumps in incoming time code.
!USB Interfaces Manual Book Page 43 Tuesday, August 16, 2011 11:21 AM