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ISUAL Flight Software Flowcharts

ISUAL Flight Software Flowcharts. Drawing 8858-T7A 9-October-2001. Overview. This document augments 8857-W7, the ISUAL Flight Software Maintenance Guide It presents a Public Domain copy of the flow charts documenting the internal tasks of the flight software. Software Tasks.

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ISUAL Flight Software Flowcharts

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  1. ISUAL Flight Software Flowcharts Drawing 8858-T7A 9-October-2001

  2. Overview • This document augments 8857-W7, the ISUAL Flight Software Maintenance Guide • It presents a Public Domain copy of the flow charts documenting the internal tasks of the flight software.

  3. Software Tasks • ISUAL Flight Software uses a non-preemptive multi-tasking system. • A task is an independent code thread, with its own stack. • Program flow switches from one task to another when a task executes a call to a function "task".

  4. Software Tasks (continued) • A call to "task" results in a switch to a new stack, and resumption of execution from where another task made a call to "task". • Interrupt service routines never change the current task, but an interrupt service routine may change the state of some data in memory, which will cause the current task to call "task"

  5. ISUAL Flight Software has 7 tasks • BG Task - Background loop • Command Task - process commands • SOH Task - SOH telemetry generator • Supply Task - Supply queue reader • DCM task - Control of the DCM • TM Task - Science telemetry PVCF generator • SC Task - Transmitter to Spacecraft • HTR Task - Operates the heaters

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