3.2.3 Command Sequences

The procedure for submitting command sequences for instrument mode changes is described in the ACIS Software User's Manual, under development by Jim Francis. Please refer there for details.

The DEA has a set of hardware settings used to condition the CCD clocks, control the analog signal processing, and set the focal plane and housing temperatures. In addition, ACIS can filter bad pixels and columns from generated CCD data and provides a set of commands for a maintainer to use to manage these settings.

Over the life of the instrument, the maintainer may issue commands to ACIS to modify its settings for various DEA clock voltages, processing levels, etc. As the CCDs degrade due to radiation damage, the maintainer may also add pixels and columns for the ACIS Bad Pixel and Column Maps. The maintainer modifies settings by issuing a ``Change System Configuration Settings'' command to ACIS. Upon receipt of this command, ACIS updates its configuration parameter block. If a Science Run is in progress when the command is executed, the changes are held until the end of the run, after which they are loaded into the hardware. If no run is in progress, ACIS immediately loads the changes into the hardware. The maintainer edits the Bad Pixel and Column Maps using ``Add'' and ``Reset'' commands. Upon receipt of these commands, ACIS modifies the appropriate map. Any changes to the Bad Pixel or Column Map will not take effect until the start of the next Science Run.

The details of these configuration commands are described in the tables below. ACIS contains a set of System Configuration Parameters, described in Table 3.9. Each parameter is identifiable using a 16-bit setting code. To change one or more of these system configuration settings, the maintainer uses a Change Settings Command, described in Table 3.10. Upon receipt of this command, ACIS overwrites the System Configuration Parameter Block items as indicated by the entries in the command packet. ACIS also provides a command which allows the maintainer to dump the current contents of the System Configuration Parameter Block. (As the System Configuration Block is at a fixed memory location, it can be dumped using the `Read BEP Memory' command.)

**Table 3.9:** System Configuration Parameter Block Content $^{\dagger}$
Item	Description
Image Section Phase Clocks - High Levels	High Level of Image Section Phase Clocks.^*
Image Section Phase Clocks - Low Levels	Low level of Image Section Phase Clocks.^*
Framestore Section Phase Clocks - High Levels	High level of Framestore Section Phase Clocks.^*
Framestore Section Phase Clocks - Low Levels	Low level of Framestore Section Phase Clocks.^*
Serial Output Register Phase Clocks - High Levels	High level of Serial Output Register Phase Clocks.^*
Serial Output Register Phase Clocks - Low Levels	Low level of Serial Output Register Phase Clocks.^*
Output Node Reset Gate - High Levels	High level of Output Node Reset Gate.^*
Output Node Reset Gate - Low Levels	Low level of the Output Node Reset Gate.^*
Output Node Reset Diodes	Level applied to Output Node's Reset Diode
Output Node Drains	Level applied to the Output Node's Drain. One entry for each Output Node on each CCD.
Output Node Output Gates	Level applied to Output Node's Output Gates
Output Node Bias Offsets	Level applied to Output Node's Bias Offsets
Scuppers	Bias-level to the Scuppers.
Back-Junction Diodes	Levels of the Back Junction Diodes.
DEA/FEP Power	On/Off
Focal Plane Heater	Set points.
Bakeout Heater	On/Off

^*The ACIS software loads these levels into the Driver board's clock conditioning Digital-to-Analog converters. There is a separately defined value for each quantity, and for each CCD.
$^{\dagger}$ Each item in this table consists of a vector of values, with each element corresponding to an individual specification for each CCD.

The command to add a set of pixels to the Bad Pixel map is described in Table 3.11. Upon receipt of this command, the ACIS software adds the listed pixels to its Bad Pixel Map. Pixel positions already listed in the map are not stored a second time. The contents of the Bad Pixel Map may be dumped into the telemetry stream via the ``Dump Bad Pixels'' command, described in Table 3.12. The result of this command is a telemetry packet, described in Table 3.13. Note that the bad pixel maps for all CCDs are sent in the telemetry packet.

**Table 3.12:** Dump Bad Pixels Command Packet
Item	Description
Packet Length	Length of command packet in 16-bit words
Sequence #	Identifies the command packet in a series.
Command Opcode	Dump_Bad_Pixels_Command opcode

Similarly, ACIS provides commands to add bad columns to the Bad Column Map. The Bad Column Map can be reset by the ``Reset Bad Columns'' command. The contents of the Bad Column Maps for all CCDs can be telemetered via the ``Dump Bad Columns'' command. These commands are described in Tables 3.14, and 3.15, respectively. A separate but similar set of commands exists for adding, removing, and dumping bad columns in Timed Exposure Mode.

To perform calibration measurements, a maintainer configures and executes one of the existing science modes described above. The ground uses the standard telemetered science data to determine the desired calibration information.