Shuttle Avionics Visual Display
SAV-O support system helps to develop displays.
The SAV-D system is composed of a display description language (DDL) and its language processor. The language provides for the description of displays in terms of static and variable references for text, special symbols, lines, and circles. Graphic displays have previously been hand-coded, using macro capabilities supplied by the manufacturer. SAV-D permits the use of a high-order English-like language to describe complete displays with increased speed and ease of coding, debugging, and modification. It also allows one to specify static and variable attributes, such as location, flash, dash, character size, and intensity. With direct communication of computers via CRT terminals and the general use of graphic displays becoming widespread, a system such as SAV-D should find many commercial applications. Although SAV-D was adapted specifically for Shuttle displays, its principles and logic could be modified for other equipment. In conjunction with appropriate CRT's, SAV-D could be used directly to develop, test, and generate end-use graphics.
The SAV-D DDL simplifies the construction of displays for the display unit (DU) CRT's used on the Space Shuttle vehicle. The language processor translates a display description written in DDL to an object program that, when executed by the display electronics unit (DEU), produces the desired display.
The object program consists of a sequence of binary format control words (FCW's) and a control interface block (CIS). The FCW's are DEU instructions for display generation. The CIS contains information required to update the generated FCW's with values that are functions of dynamic data available at the time the FCW's are loaded or being executed in the DEU memory. Inputs to the SAV-D language processor are a source program written in DDL and an optional DEU character-set reassignment file . The source program may contain two types of DDL statements. Normal SAV-D statements permit the programer to describe a display symbolically, without concern for the instruction set available on the DEU. Symbolic FCW statements permit direct programing of the hardware by providing a facility to express FCW's to be executed by the DEU. SAV-D assigns a CRT symbol and symbol name to each hexadecimal DEU code . The programer may override these assignments, either selectively or completely, by supplying his own reassignments . The reassignment consists of a symbol name and single character code representation (if one exists) for each hexadecimal DEU code to be reassigned.
The language processor outputs an executable object program, directives for real-time modification of the program, and listings that help to resolve problems with unsatisfactory displays. The object program is loaded in the DEU memory, is updated with real-time values, and is executed to produce the desired display. The DEU in the Space Shuttle system interfaces the ISM AP101 with the Multifunctional CRT Display System (MCDS).
The SAV-D program is written in FORTRAN IV for execution in the batch mode and has been implemented on an ISM 370 1165 with a central memory requirement of approximately 500K (decimal) of 8-bit bytes.
This program was written by Arthur A. Yoshimura of Rockwell International Corp. for Johnson Space Center. For further information, Circle E on the COSMIC Request Card. MSC-16591
NASA Tech Briefs, Summer 1977
I still don't have the full picture of how the signals are made available in the GPCs and how they can fail in there, to use the (small) knowledge I have about RM. There are 2 new displays that show the signals from RHCs and THCs, but the channel deselection capability is not used.
