Lexicon PCM 81 - REV, User Manual

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2-5
Basic Operation
When External clock is selected, any loss of lock detected in the incoming digital
audio, or reception of non-audio data will cause the PCM 81 to immediately mute
the digital input, and switch to Internal clock at the sample rate of the last valid
external signal. An error message will be displayed if this occurs. The PCM 81
will continuously try to re-establish lock, returning automatically to External clock
if and when lock is confirmed.
The following types of errors are detected when the PCM 81 is set to Ext:
No Lock: The PCM 81, 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 81 digital input. This display is active even when the PCM 81 is set to
Internal clock. Note that in the case of an AES Pro format signal, "Emp:Yes"
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 81 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 81 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 81 is detecting excessive jitter or noise on the digital
audio line. No data has been corrupted, but corrective action
should be taken.
SlipSample: Indicates that a single sample is misaligned with the window
defined by the Word Clock. This may occur when an external
master changes sample rate, or when it is just powering up, but
should not occur in normal operation.
CRC: Indicates a Cyclic Redundancy Check error in the incoming data.
Upon loss of lock, or reception of non-
audio data, the PCM 81 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