Description

The Watchdog tasks collect and evaluate information from other tasks. If the information indicates the presence of a problem, they call a "bug check" mechanism. In addition, they issue the CPU's "heartbeat". If the hardware watchdog does not receive this on a timely basis, it will initiate a hard reset of the CPU's crate.

The Master receives requests for software watchdog change-of-state requests, redistributing them to each targeted Slave.

Each Slave implements the software watchdog function for its CPU (e.g., interrogating Registered Tasks for progress). In passive mode, the Slave always refreshes the hardware watchdog. In active mode, the Slave only refreshes the hardware watchdog if all subsystems report progress; otherwise, it performs a "warm boot".

The Watchdog subsystem supports two data paths:

• Slave Loop

  The Slaves run Diagnostic routines on the local RAM. They send Inquiry messages to Registered Tasks, accepting the Response messages. Finally, if all is well, they send periodic messages to the Hardware Watchdog.

• Spacecraft Command

  The Spacecraft sends change-of-state request Commands to the Master, which forwards them to the Slaves.

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