The ABC of XTE: EDS Flags and Coda

EDS Flags and Coda

EDS Flags: Spillage, ModeSpecific, Lost Events

In addition to columns for time and binned events, PCA science array files also contain columns for flags called Spillage and ModeSpecific. In science event files, these flags appear in the Event column as alternative event word templates, with the addition of the LostEvents flag

Spillage is used to flag instances when the EDS received more events than it could process and more than zero events were dropped. If no spillage occurred, its value is zero. If spillage occurred in the previous accumulation, then its value is 1.

LostEvents (in Event Mode only) contains the number of events that did not fit into the buffer anymore. Beware, it's an unsigned short and may have rolled over.

ModeSpecific is only meaningful for Trigger modes. It contains the three trigger flags: low, high and HEXTE.

EDS Coda

Before a new PCA configuration is run by an Event Analyzer, the EDS ends the old run by attaching a coda. The coda contains information about the status of the EDS during the run, including errors and discrepancies between what was processed and what was recorded and telemetred.

The various pieces of coda information end up as keywords at the end of the header of the XTE_SA extension. They are prefaced by the DDESC keyword which contains a DDL string indicating the origin of the coda. For example:

O[XTE] & I[EDS] & D[0] & E[EA1]

shows that the coda in question refers to EA1 on the "A" side of the EDS. Next come the individual coda items comprising:

ConfigId: This field is identical to the Configuration Id in the Parameter Block used by the observation.
EARunStart: This specifies the actual (as opposed to scheduled) starting time of the observation (in MajorTicks).
PartCount: This specifies how many partitions of data were generated (but not necessarily telemetered) by the observation.
TyperErrCount: This is the total number of discrepancies between the encoded Typer Table and the actual Typer Table, after the observation (Value has meaning for PCA Modes Only).
TyperErrOffset: This identifies the Typer Table offset which contained the first discovered discrepancy (Value has meaning for PCA Modes Only).
TyperErrValue: This identifies the value that was read at the Typer Table offset, which didn't match the encoded table (Value has meaning for PCA Modes Only).
RecodErrCount: This is the total number of discrepancies between the encoded Recoder Tables and the actual Recoder Table, after the observation (Value has meaning for PCA Modes Only).
RecodErrOffset: This identifies the Recorder Table offset which contained the first discovered discrepancy (Value has meaning for PCA Modes Only).
RecodErrValue: This identifies the ,value that was read at the Recoder Table offset, which didn't match the encoded table (Value has meaning for PCA Modes Only).

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The ABC of XTE is written and maintained by the RXTE GOF. Please email xtehelp@athena.gsfc.nasa.gov if you have any questions or comments. This particular page was last modified on Tuesday, 14-Sep-1999 13:45:41 EDT.