Lambda SR1, Руководство по эксплуатации, Страница: 185 / 317

SR1 Operation 185
© 2014 Stanford Research Systems
Xmit Block Triggers on the transmission of a block preamble (Z-preamble) by the digital audio
output generator.
Ref Out
Preamble A Triggers on the transmission of a channel A subframe preamble (X-preamble) at the
digital audio reference output.
Ref Out
Preamble B Triggers on the transmission of a channel B subframe preamble (Y-preamble) at the
digital audio reference output.
Ref Out Block Triggers on the transmission of a block preamble (Z-preamble) at the digital audio
reference output.
Generator Triggers on the receipt of a generator trigger. (See the Analog and Digital generator
sections)
External (rising) Triggers on the rising edge of a signal at the rear-panel external trigger in connector.
External
(falling) Triggers on the falling edge of a signal at the rear-panel external trigger in connector.
Error Trigger Conditions
The "Error Trigger" triggers on the receipt of any of the following error conditions detected in their
respective input streams:
CRC For AES/EBU digital audio streams an 8-bit CRC code is generated from the received
channel status bits in each block and compared to the value stored in the last byte of the
channel status block. A CRC error occurs if these values do not match.
Lock An error occurs if the digital audio receiver on the given connector cannot lock to the input
signal.
Validity An error occurs if the validity bit is set on either subframe of the received or transmitted
signal.
Coding Bi-phase coding error. The error occurs if the carrier signal remains at the same level for
greater than 2 unit intervals (other than during preambles.)
Parity An error occurs if the computed parity of each subframe does not match the parity bit
contained in that subframe.
Post Trigger Length
For all trigger sources except auto trigger, the user can specify the fraction of the total digitizer record
that occurs after the occurrence of the trigger. A post trigger fraction of 100% means that the trigger
occurs at the very beginning of the record while a fraction of 50% means that the trigger occurs precisely
in the middle of the record. This features enables examination of signal features that occur pre-trigger.
For the "Auto" trigger selection, the post-trigger length is always set to 100%.
Digitizer Analysis Controls
After acquisition, the digitizer examines the input time record and makes a preliminary estimate of the
zero-crossing positions and the unit-interval time. For a digital audio signal, all transitions should either