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STEbus 48×16 and 80×20 character text

Video generated by an AMD 2910 bit-slice controller

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The SVA and SVB used an AMD 2910 bit-slice controller chip to generate the video address sequences.
IC7 contains the sequencing program. IC8 is 2K of video RAM, write-only to the STEbus.
IC9 is the font ROM.
Essentially the same board with different ROM data, the SVA was 16 lines × 48 characters with graphics and the SVB was 20 lines × 80 characters with inverse video. They were superseded by the SVC video board.

Alas I don't have any more information than the catalogue page and pictures. I wasn't motivated to grab it because it was not very impressive.

zpekic asked if it was inspired by the design in the book Bit Slice Microprocessor Design, pages 47-89. I think it probably is, because you would not use this chip unless you were promoting the use of these chips.

However, if you are interested in how this board worked, the book would be a great place to start.

The book design seems much more complex than the SVA/SVB boards. It is switch-programmable for multiple video formats. The SVA/SVB boards were designed for industrial applications, where a simple fixed text display format was adequate. 

Note that the files uploaded here are from the book design. They have been assembled by a clone of the AMD bit-slice assembler written by Holger Veit. The fact that they assemble just means the gross errors introduced by OCR have been weeded out. The output has not been tested on any hardware, because I don't have any.

Holger's assembler was very easy to get working. Download the code, modify a couple of lines in the makefile for Linux type machines, then run make. That generates an executable that you can use straight away. If you have a project called CRT then the usual expectation is file called  CRT.def and CRT.src then you just type

 ./amdasm CRT

Arcom J040 SVA-B parts list.txt

All the ICs. No programmable logic, which is unusual.

plain - 641.00 bytes - 02/09/2025 at 13:57

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CRT.def.txt

CRT.def Definition Files for the CRT Controller.

plain - 661.00 bytes - 02/03/2025 at 06:57

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CRT.src.txt

CRT.src Assembly Files for the CRT Controller.

plain - 10.93 kB - 02/03/2025 at 06:57

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CRT.p1l.txt

Assembler Phase 1 output.

plain - 922.00 bytes - 02/03/2025 at 06:57

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CRT.p2l.txt

Assembler Phase 2 output.

plain - 20.28 kB - 02/03/2025 at 06:57

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View all 8 files

  • Catalogue page

    Keith11/04/2021 at 11:49 0 comments

    SVA,SVB

    These video controller boards provide a low-cost means of displaying video on STEbus systems. Two versions are available: the SVA which provides a 48-character × 16-line display, or the SVB which offers 80-character × 20-lines.

    SVA comes with 128 ASCII characters and 128 graphics symbols suitable for industrial displays; these include lines, pipes, junctions, bar graph or histogram characters and even a man with a spanner.

    SVB is designed for information processing applications and offers an inverse video character set in addition to standard ASCII. Characters are stored in EPROM. allowing you to define your own 256-character set on an 8 × 16 matrix. The board’s fast 2910 bit-slice controller provides a completely flicker-free display; 2k of screen memory is included.

    Both video output and composite video and sync outputs are provided. We can also supply 5-inch monitors (which fit into a 3U rack, including a version with a touchscreen interface.

    STEbus:

    The board implements a write-only slave interface to the bus. It can be memory-mapped into any 4k segment of the bus memory space.

    Power Consumption:

    typically 0.7A at 5V

    Features:

    • 48 characters × 16 lines with graphics
    • 80 characters × 20 lines with inverse video
    • 256 user-programmable 8 × 16 matrix characters
    • Completely flicker-free image display

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