Specifications

Chapter 5: Additional Operational Information 63
Calibrating the SYNC I/O
Oscillator
SYNC I/O provides a feature for calibrating the
frequency of the on-board crystal oscillator.
This allows SYNC I/O to be used as an extremely
accurate frequency reference while in Inter-
nal/VSO mode.
With normal usage, SYNC I/O should never re-
quire recalibrating. Each unit is factory cali-
brated to within +/– 5 ppm (parts per million).
You may want to recalibrate SYNC I/O in the
following situations:
• If greater than 5 ppm accuracy is required.
• If the unit needs to be matched to a unique
(nonstandard) frequency.
•To precisely compensate for component ag-
ing.
– and –
•To restore the original factory setting.
Oscillator Resolution and Stability
SYNC I/O calibration units are in 1/64th of a
sample period. What this means is that
SYNC I/O can theoretically be calibrated to
about 1/3 of a ppm. The unit will maintain cali-
bration across a wide range in temperature.
Long-term drift should be less than 1 ppm per
year due to aging of the crystal. To put this in
perspective, most digital audio products are ac-
curate to within 20 to 50 ppm and drift with
temperature. SYNC I/O’s accuracy is possible be-
cause it contains a low-jitter, high-stability tem-
perature controlled crystal oscillator.
Warm Up SYNC I/O Before Recalibrating
Before you begin the calibration procedure,
power on SYNC I/O and allow it to warm up for
at least five minutes. The temperature of the
room (or chassis) isn’t critical during the calibra-
tion procedure. However, if you need better
than 3 ppm accuracy, it is recommended that
you allow SYNC I/O to warm up for at least 30
minutes and that the chassis be at normal oper-
ating temperature.
The original Oscillator Calibration value is
printed on the factory sticker, on the SYNC I/O
bottom panel.
To restore the SYNC I/O oscillator calibration to
its factory setting:
1 Press Set, then press Up until Video System
(VIdEo SY) is displayed in the LED readout.
2 With the LED Time Code Display showing
VIdEo SY, press and hold the Up switch. While
you continue to hold that switch, press the
Clock Reference switch momentarily, and then
release both switches. The LED Time Code Dis-
play will read:
3 Press Set again. The LED Time Code Display
shows the current parameter value, which
shows a sample rate frequency deviation from
–0999 to 0999.
4 Take note of the Oscillator Calibration value
printed on the factory sticker, on the SYNC I/O
bottom panel.
5 Use the Down and Up switches to scroll
through the parameter values.
Oscillator recalibration does not occur dur-
ing firmware updating or when resetting
SYNC I/O to factory defaults (see “Restoring
Factory Settings” on page 64).