Command/Response

Master tasks on the SIU engage in dialogs with the CRU (Command/Response Unit, in the GASU), for the purposes of instrument configuration and interrogation.

Data to SSR

Tasks send various kinds of data (e.g., housekeeping, science) to the SSR (Solid State Recorder) for storage and eventual transmission to Earth.

Master to slave

Master tasks schedule the duties of their slave tasks by queuing messages.

Physics data from LAT

The LAT sends physics data to the Event Builder (in the GASU), for assembly into events. These are sent to the Instument Physics slave tasks, for processing.

Slave to Master

Slave tasks provide their masters with responses (e.g., statistics, status) by queuing messages.

Telecommand

Telecommand packets are received from the Spacecraft, via the 1553 data bus. Each packet is routed, based on its APID (Application ID number), to the appropriate task.

Telemetry

Telemetry packets are generated by tasks, then sent to the Spacecraft via the 1553 data bus.