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ACIS provides the maintainer with a measure of how the ACIS system is operating. This information includes the disposition of commands, statistics on various operating conditions, the current state of the instrument, and fatal error indications.
In order to help a maintainer develop a history of the operation of ACIS, the ACIS Science Instrument Software maintains and telemeters software housekeeping information. Whenever an observer or maintainer sends a command to the ACIS Science Instrument Software, ACIS posts an echo of the command and its disposition to telemetry. This allows an maintainer to verify that all commands intended for ACIS software were received and interpreted.
In order to allow monitoring of the overall operation of ACIS without relying on its serial science telemetry, ACIS also provides active status information using the discrete telemetry signals, read by the hardware and placed into the Engineering portion of the telemetry stream (see Section 3.1.4.5 on page 36).
ACIS shall provide command receipt and disposition indication in the telemetry stream. After processing each ACIS command, the software will form and post a telemetry packet which contains the Back End timer-tick value at the time the command was received, a result code indicating the disposition of the command, and a verbatim copy of the received command packet.
TABLE 63. Command Echo Telemetry Content (Continued)
------------------------------------------------------------------------------------------------ Req Item Description------------------------------------------------------------------------------------------------ 63-1 Packet Synch This field marks the start of the ACIS packet within the telemetry stream. 63-2 Packet Word Length This field indicates the number of 32-bit words in the packet. 63-3 Format Tag This field indicates the type of data contained in the teleme try packet. 63-4 Packet Sequence Number This field is used to sequentially number all ACIS telemetry packets. 63-5 BEP Tick Counter This item contains the value of the internal timer-tick counter at approximately the time at which the command packet was received by the software. 63-6 Command Result Code This is the disposition code of the command. These codes shall be capable of representing the following types of condi tions: Command executed successfully without warnings or errors Command was not executed (code must indicate reason) Command executed with warnings (code must indicate rea son) Command executed with errors (code must indicate reason) 63-7 Copy of Command Packet This is a copy of the command packet received by the ACIS software ------------------------------------------------------------------------------------------------
The ACIS software shall indicate its boot and running status using the 4 discrete telemetry signals provided by the ACIS hardware (see Section 3.1.4.5 on page 36).
During boot, these signals shall indicate the current mode of the boot and current state. If, ACIS hangs during the boot, the boot status shall provide an indication of the last action performed prior to the lockup.
While running after a commanded reset, the ACIS software shall cycle the signals between two or more values, indicating the current overall state of the software. If ACIS hangs, these signals will freeze into one state until the Watchdog Timer resets the system.
After a watchdog reset, ACIS shall cycle these signals between values which indicate that ACIS had locked up at some point, and was reset by the Watchdog Timer.
ACIS shall maintain a set of system statistics representing various operating conditions, such as number of interrupts, numbers of context switches, etc. These statistics also contain the number of occurrences of various warning conditions, such as the number of dropped exposures. These statistics shall be represented as an array of counters. Periodically, ACIS shall telemeter and reset the contents of these statistic counters. Table 64 illustrates the content of a statistics packet.
TABLE 64. Software Housekeeping Telemetry Content (Continued)
----------------------------------------------------------------------------------------------------------- Req Item Description----------------------------------------------------------------------------------------------------------- 64-1 Packet Synch This field marks the start of the ACIS packet within the telemetry stream. 64-2 Packet Word Length This field indicates the number of 32-bit words in the packet. 64-3 Format Tag This field indicates the type of data contained in the telemetry packet. 64-4 Packet Sequence Number This field is used to sequentially number all ACIS telemetry packets. Since this is the first packet which is sent after a reset, this field will be zero. 64-5 BEP Tick Counter This items contains the value of the internal timer-tick counter at approximately the time (i.e. within a minute) when accumulation into the packet started. The remainder of the packet contains the set of software statistics reported since the previous housekeeping packet was sent, or since the Back End Processor was re-booted. Each statistic is reported using a statistic identifier, count of reports since the previous housekeepng packet, and the most recently reported value associated with the statistic (NOTE: For some statistics, this third item is always zero). The number of values and slot assignments are listed in the ACIS Software IP&CL Structures Definitions (MIT 36-53204.0204). 64-6 Statistic Identifier This identifies the item being reported in this entry. 64-7 Counter Value This contains the number of times a particular statistic was reported since the last time a software housekeeping packet was sent, or since the instrument was reset if this is the first housekeeping packet. 64-8 Counter Argument This contains the last reported statistic argument value. -----------------------------------------------------------------------------------------------------------
Both the ACIS Back End and Front End software shall periodically set their respective Watchdog Counters (see Figure 10, "Mongoose Component Overview," on page 30). The value written into the counter determines the time-out duration of the Watchdog Timer. In the event of a crash whereby the ACIS software hangs, the Watchdog Timers will reset the hung processor.
Upon reset, after the instrument software has been initialized and is running, the ACIS software shall post a startup telemetry packet, indicating the cause of the restart. Table 65 illustrates the content of this packet.
TABLE 65. Startup Telemetry Content (Continued)
--------------------------------------------------------------------------------------------------------- Req Item Description--------------------------------------------------------------------------------------------------------- 65-1 Packet Synch This field marks the start of the ACIS packet within the telemetry stream. 65-2 Packet Word Length This field indicates the number of 32-bit words in the packet. 65-3 Format Tag This field indicates the type of data contained in the telemetry packet. 65-4 Packet Sequence This field is used to sequentially number all ACIS telemetry packets. Number Since this is the first packet which is sent after a reset, this field will be zero. 65-5 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 packet is sent. 65-6 Reset Reason Code This indicates the reason the instrument reset. This code specifies either a Commanded Reset, or a Watchdog Reset. 65-7 Startup Information These items describe the state of the instrument at start-up, such as the version number of the software, the most recent fatal error mes sage code and value, the states of the patch list, system configuration parameters, and stored parameter blocks. ---------------------------------------------------------------------------------------------------------
If ACIS encounters a condition from which it cannot recover, it shall make a best attempt to flush the current telemetry packet being written to the RCTU, and then issue a telemetry message indicating that ACIS is about to reset. After sending this message, the software uses the Watchdog Timer to reset the instrument within at most 7 or 8 minutes (NOTE: The time-out will probably set to around 10 seconds to improve testability). Table 66 illustrates the content of this error message.
TABLE 66. Fatal Error Telemetry Content (Continued)
---------------------------------------------------------------------------------------------------- Req Item Description---------------------------------------------------------------------------------------------------- 66-1 Packet Synch This field marks the start of the ACIS packet within the telemetry stream. 66-2 Packet Word Length This field indicates the number of 32-bit words in the packet. 66-3 Format Tag This field indicates the type of data contained in the telemetry packet. 66-4 Packet Sequence This field is used to sequentially number all ACIS telemetry packets. Number 66-5 BEP Tick Counter This items contains the value of the internal timer-tick counter at approximately the time (i.e. within a minute) when fatal condition was reported. 66-6 Fatal Error Code This indicates the point at which the fatal error was detected. 66-7 Optional Argument This item is provided to allow more information about the error to be telemetered. This meaning of this item depends on the Fatal Error Code. ----------------------------------------------------------------------------------------------------
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