Lexicon PCM 80 User Manual
Page 23
2-5
Basic Operation
When External clock is first selected, the PCM 80 will repeatedly try to establish
lock. You can choose to have any subsequent interruptions of the incoming
digital audio signal dealt with in one of two ways. An Auto Lock feature allows
you to choose to have the PCM 80 attempt to re-establish lock, or not. (See 0.3
Auto Lock.) In either case, the PCM 80 will immediately mute the digital input,
and switch to Internal clock at the sample rate of the last valid external signal.
When External clock is selected, any loss of lock detected in the incoming digital
audio, or reception of non-audio data will cause the digital input to be muted. An
error message will be displayed if this occurs.
The following types of errors are detected when the PCM 80 is set to Ext:
No Lock:
The PCM 80, at some point, lost lock to the incoming digital
audio signal. Digital audio input is muted.
Out of Range:
The sampling rate of the incoming audio signal is outside of
acceptable tolerance limits of +4%. Digital audio input is
muted.
Non Audio:
Indicates transmission of non-audio data, such as from a CD
ROM. Digital audio input is muted.
Dig In Status
Pressing Load/
✱
from Word Clock will display the current digital input status.
This status display is continuously updated, acting as a real-time monitor of the
PCM 80 digital input. This display is active even when the PCM 80 is set to
Internal clock. Note that in the case of an AES Pro format signal, "Emphasis"
means either CCITT or 50/15µs emphasis.
If valid digital audio is detected, the display will show the external clock rate and
format information, along with the status of the Emphasis bit(s) in the incoming
audio signal. If the PCM 80 has lost lock, the display message will indicate "No
Lock" and parenthetically show the internal clock rate now in use.
Audio *Dig In Status
0.0 Prf 44.1 Emp:Yes
Audio *Dig In Status
0.0 NoLock (Int:44.1)
When the PCM 80 loses lock, it will mute the digital input and switch to Internal Clock.
Error Log
The following errors are continuously logged and are available for review by
pressing Load/
✱
from the Dig In Status display and using ADJUST to scroll
through the error list.
Validity:
A Validity error indicates that the Validity bit was set in a frame
of incoming data and that the data attached to it may be
corrupted. This bit may also be sent when the transmitting device
is paused.
Confidence:
The PCM 80 is detecting excessive jitter or noise on the digital
audio line. No data has been corrupted, but corrective action
should be taken.
Upon loss of lock, or reception of non-
audio data, the PCM 80 will mute the
digital input and display the following
messages when Word Clock or Dig In
Status is selected:
Word Clock
Dig In Status
Not Locked
No Lock (Int 44.1)
Out of Range
No Lock (Int 44.1)
Non Audio: 44.1
Non Audio: 44.1