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PAL-1 Colour Video Card

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PAL-1 Sprite Colour Graphics Adapter

The PAL-1 Sprite Colour Graphics Adapter is an expansion board for the PAL-1 system1, based on the Texas Instruments TMS9918A Video Display Processor (VDP)2 and was inspired by a Ciarcia's Circuit Cellar project3.

The TMS9918A VDP was used in video systems to provide data display on raster scanned colour television sets or monitors. The IC generates all necessary video, control, and synchronisation signals and also controls the storage and retrieval of display data in its own dedicated screen memory.

Note
The TMS9918A VDP generates a 525-line NTSC encoded colour video signal. While the TMS9928A VDP, which is intended for use with PAL video systems, is functionally compatible with the TMS9918A, it is not pin-for-pin compatible. Thus it is not possible to use the TMS9928A VDP in the PAL-1 Sprite Colour Graphics Adapter. Instead, users who do not have access to an NTSC TV or monitor are recommended to use AV to HDMI or AV to VGA converters as appropriate. Such converters are widely available from the usual e-commerce and auction web sites.

Acknowledgements

The SRAM circuitry is based on work by Tom LeMense and Dan Werner4,5.
PAL-1 and the PAL-1 logo used with kind permission of Liu Ganning.

References

  1. Liu Ganning, ‘PAL-1 Microcomputer User Manual’, 2020 http://pal.aibs.ws/assets/PAL_en.pdf [accessed 21 July 2022].
  2. ‘9900 TMS9918A/TMS9928A/TMS9929A Video Display Processors’ (Texas Instruments Incorporated, 1982) https://web.archive.org/web/20180717212934/https://emu-docs.org/VDP%20TMS9918/Datasheets/TMS9918.pdf [accessed 17 September 2022].
  3. Steve Ciarcia, ‘High-Resolution Sprite-Oriented Color Graphics’, Byte, 7.8 (1982), 57–80.
  4. Tom LeMense, ‘SRAM Replacement for TMS99x8 VRAM’, 2010 https://retrobrewcomputers.org/n8vem-pbwiki-archive/0/35845334/48860720/33053543/SRAM%20Replacement%20for%20TMS99x8%20VRAM.pdf [accessed 17 September 2022].
  5. Tom LeMense and Dan Werner, ‘Video Display Interface Board’, RetroBrew Computers Wiki, 2021 https://www.retrobrewcomputers.org/doku.php?id=boards:ecb:scg:start [accessed 17 September 2022].

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PAL-1 Colour Video Card