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A maintainer will wish to periodically monitor various Detector Electronics Assembly operating values. ACIS provides commands allowing the maintainer to select which values to monitor, and to start and stop the monitoring process. Some of these housekeeping values are coupled to specific CCDs. As a result, some flexibility is needed, in respect to which housekeeping values are to be sampled.
ACIS DEA Housekeeping Runs can execute concurrently with and are similar in nature to Science Runs. To perform a DEA Housekeeping Run, the maintainer commands ACIS to accept a parameter block containing a list of DEA registers to sample, and then instructs ACIS to execute the run. ACIS first dumps the parameter block into the telemetry stream, and then proceeds to sample the specified items by issuing queries to the DEA and storing the responses. ACIS then telemeters the set of sampled values. The maintainer allows ACIS to continue its data acquisition for the desired period of time and then commands ACIS to terminate the run.
ACIS shall maintain one or more lists of DEA Housekeeping items to monitor. The maintainer installs this list by issuing a "Load DEA Housekeeping Parameter Block" command., and selects which list to use for a run via the "Slot Id" field of the list. Table 67 illustrates this command.
TABLE 67. Load DEA Housekeeping List Block Command Packet (Continued)
-------------------------------------------------------------------------------------------------------- Req Field Name Description-------------------------------------------------------------------------------------------------------- 67-1 Packet Word Length This indicates the total number of 16-bit words in the command packet. 67-2 Packet Identifier This identifies the command packet. 67-3 Command Opcode "Load DEA Housekeeping Parameter Block" command opcode. This instructs the ACIS software to store the List Data contained within the packet. 67-4 Slot Id This identifies the block within ACIS. 67-5 Block CRC or Checksum This is used to check the load. 67-6 Parameter Block Identifier This item is a ground-supplied identifier which is echoed by the instrument software in the DEA housekeeping telemetry. 67-7 Sampling Rate This specifies the rate at which ACIS should sample and teleme ter the acquired information. It is specified in terms of number of seconds between item samples. This parameter can range from 1 to 64 seconds. 67-8 DEA Item List The remainder of the packet contains the list of DEA items to sample. --------------------------------------------------------------------------------------------------------
ACIS shall accept and process "Start DEA Housekeeping Run" commands. Table 68 describes the format of this command.
TABLE 68. Start DEA Housekeeping Run Command (Continued)
------------------------------------------------------------------------------------------------- Req Field Name Description------------------------------------------------------------------------------------------------- 68-1 Packet Word Length This indicates the total number of 16-bit words in the command packet 68-2 Packet Identifier This identifies the command packet in a series. 68-3 Command Opcode "Start DEA Housekeeping Run" command opcode. This instructs the ACIS software to retrieve the parameter block indicated by "Slot Id" below, and run the requested DEA Housekeeping operation. ACIS will continue to run the operation until commanded to stop. 68-4 Slot Id This identifies the DEA Housekeeping Parameter block to use for the run. This block may have been loaded just prior to the Start Run command, or may be part of either the pre-loaded library, or one of the blocks provided at launch. -------------------------------------------------------------------------------------------------
Upon receipt of this command, ACIS shall dump the contents of its parameter block into to the telemetry stream, and then start sampling and telemetering the items as specified by the parameter block.
ACIS shall accept and process "Stop DEA Housekeeping Run" commands as described above. Table 69 describes the format for a generic "Stop DEA Housekeeping" command.
TABLE 69. Stop DEA Housekeeping Run Command (Continued)
------------------------------------------------------------------------------------------- Req Field Name Description------------------------------------------------------------------------------------------- 69-1 Packet Word Length This indicates the total number of 16-bit words in the command packet 69-2 Packet Identifier This identifies the command packet in a series. 69-3 Command Opcode "Stop DEA Housekeeping Run" command opcode. This instructs the ACIS software to stop the current run. -------------------------------------------------------------------------------------------
Upon receipt of this command, ACIS shall stop sampling and telemetering DEA Housekeeping information.
During a DEA Housekeeping Run, the ACIS software shall report the acquired DEA register values. Table 70 illustrates the content of this telemetry.
TABLE 70. DEA Housekeeping Telemetry Content (Continued)
-------------------------------------------------------------------------------------------------------------------- Req Item Description-------------------------------------------------------------------------------------------------------------------- 70-1 Packet Synch This field marks the start of the ACIS packet within the telemetry stream. 70-2 Packet Word This field indicates the number of 32-bit words in the packet. Length 70-3 Format Tag This field indicates the type of data contained in the telemetry packet. 70-4 Packet Sequence This field is used to sequentially number all ACIS telemetry packets. Number 70-5 Command Packet This is the packet identifier of the start command which initiated the Identifier current run. 70-6 BEP Tick Counter This items contains the value of the internal timer-tick counter at approximately the time (i.e. within a minute) when the data contained in the packet was started to be acquired. 70-7 The remainder of the packet contains a list of DEA Housekeeping Entry pairs. The number of entries is determined using the packet length: 70-8 Item Identi This value uniquely identifies the DEA Housekeeping fier item being sent 70-9 Item Value This is the value of the acquired DEA Housekeeping item. --------------------------------------------------------------------------------------------------------------------
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