ATAC: Ada Tasking in Hardware

The Ada TAsking Coprocessor (ATAC) is a hardware component (ASIC) in charge of the Ada tasking on behalf of the software run-time system of the compiler. In the ATAC2.0 chip, the full Ada83 tasking semantic (plus the semaphore, the delay_until and the Basic Priority Inheritance protocol) is implemented in hardware through 64 high level instructions. ATAC is typically in charge of the computation of the task dependency tree and the computation of the next task to be scheduled. It supports the suspend/abort statements, the delay statement and all types of rendez-vous. It handles the priority and interrupts. It provides semaphore and detects and propagates tasking related exceptions.

ATAC can be accessed either by a specific software layer written in assembly language for this purpose and interfacing the application software (as for AXS), or by the Ada compiler itself (as the TLD one). The latter way is fully transparent to the user.

If you are in a hurry, just go directly to the list of potential benefits that the ATAC will bring to your application.

Hardware Presentation

An introduction to the ATAC hardware features, including:

the hardware interface;
the interrupts management;
the time management;
the ATAC memory;
the priority management;
the ATAC clock.

Software aspects of the ATAC

An overview of the ATAC instruction set, and two scenarios for the ATAC/CPU dialogue

Some figures about the ATAC performance

The ATAC performance and the resulting benefits for an application are detailed here:

some considerations about the level of measurement;
figures related to the Ada mechanisms;
a nice curve showing the ATAC improvements against the complexity of some Ada constructs;
a list of the identified advantages that ATAC can bring to your application.
(All figures courtesy of R-Tech.)

The ATAC program overview

The ATAC related activities, including:

a little bit of history;
the ATAC-based boards;
the ATAC-based AXS Operating System;
the ATAC-interfaced compilers;
the rad-hardened chip ATAC2.1x;
various other activities.

The documentation available on ftp

Various documents are to be found on the ftp site (Format: PostScript) including:

the reports of the ATAC evaluation performed by industry;
the executive summary of the ATAC day (Nov 16th, 95);
a curve showing the ATAC improvements against the complexity of some Ada constructs;
etc...

This is what you should think about the ATACa after reading this text!

This page is maintained by the Spacecraft Control and Data Systems Division, WS, at ESTEC (European Space Research and Technology Centre). Contact point:

Jean-Loup TERRAILLON (jeanloup@wd.estec.esa.nl)

The ATAC has been designed by R-Tech AB, Surbrunnsgatan 60, S-113 27 STOCKHOLM Sweden. Phone & Fax +46-8-331920. Contact person: Joachim Roos (joachim@r-tech.se)

Questions related to the TLD compiler can be directed to them, 3625 Del Amo Blvd., Ste. 100 Torrance, California 90503, USA. Phone +1-310-542-5433, Fax +1-310-542-6323, e-mail Terry Dunbar (tld_ptr@cerf.net)

Last edited 28 November 1995

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