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Basic Operation
PCM 91
Input Source 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
Error Log
• CRC: Indicates a Cyclic Redundancy Check error in
the incoming data.
• Parity, Indicate that at least one bit (and therefore at
Biphase: least one audio sample) was corrupted.
Parity, Biphase, and Confidence errors are most often caused by
inappropriate cabling. Be sure to use 75Ω video-grade cable, kept
as short as possible — standard audio cable will not work reliably.
Each error is reported by name, with the number of occurrences of
that particular type of error. The display might show, for example
"CRC: 4752". As many as 9999 instances of each error can be
shown. If the number of actual errors exceeds 9999, the display will
indicate ">9999". A special symbol (n) before the error type
indicates the most recently received error.
Audio ✱Error Log
0.0 ■ CRC >9999
Press Load/✱ from the Dig In Status display and use ADJUST to scroll through the Error Log.
A typical Error Log display showing that the
last error received was a CRC error (
■
CRC)
and that there have been more than (>)
9999 instances of CRC errors since Word
Clock was last set to Ext.
When the PCM 91 loses lock, it will mute the digital input.
Audio ✱Dig In Status
0.0 Prf 44.1 Emp:Yes
Audio ✱Dig In Status
0.0 No Lock (Int:44.1)
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 91 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 Input Source.
This may occur when an external master
changes sample rate, or when it is just
powering up, but should not occur in normal
operation. (This type of error is reported for
reference only, as the PCM 91 does not accept
digital data when using its own internal clock.)
To clear the Error Log, reselect Dig from the Control Mode Input
Source display. This will cause the PCM 91 to attempt to lock to the
current external source and will reset the Error Log. The log is also
cleared on power up, and whenever it relocks (Auto Lock On).
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