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Showing results for tags 'TMS9918'.
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Info from one of the designers of the Texas Instruments video chip that was famously used in the TI-99. ColecoVision, SEGA SG-1000, MSX, and many other game consoles and computers: "We were about the cancel the whole 9918 program when Coleco came in with Colecovision and the TI Home Computer took off while at the same time the MSX computer in Japan (the “MS” standing for Microsoft which had a short lived joint venture in Japan) started selling big time using the 9918." "there is a color burst at ~3.58MHz. The 9918’s input clock was ~10.74MHz or exactly 3 times the color burst reference." http://msx.hansotten.com/technical-info/tms9918/
HELP! I've been working on this project: http://github.com/calphool/TRS80GS I've built 4 revisions of this board for my friend's TRS-80. I've had a heck of a time keeping the VDP chip working in a stable configuration. I had everything working for a while, and then suddenly it decided that it wouldn't work any more. I screwed around with the caps on the crystal (soldering on heavier leads and stuff), and eventually it blinked back to life, but now I only have a luminance signal (or at least the TV can't interpret the color part of the NTSC signal, so I get black-and-white). What I need is a very stable clock, and unfortunately there seem to be about a half dozen different examples of how people have set up the clock on this chip. Here are a few: I need something that just always works, not something that's flaky and subject to weird transient noise. The VDP and its clock divider are basically the heart of my board now, and if I can't get the clock working right, nothing works (the sound chips and UART chip use the divided clock signal that comes out of the VDP for their own clocks). What's the best way to make sure this clock is super stable and reliable? The Texas Instruments hardware design? It's got a bunch of stuff inline (including something it calls an "SR Inductor" that has no uH rating, and I'm a little confused by). The ChromaTRS design? It's got some inverter gates attached to the crystal (though it doesn't specify the value for the resistor it's using). I've been using variations on each revision, with the most recent being the one from Byte magazine, which is flaky as all get out.
Does anyone know what the recommended saturation level should be regarding the TMS9928A VDP as used on the ColecoVision? I have played around with various values like 0.47 (same as the value used for the R-Y and B-Y values of the neutral colors and which makes the TMS9928A colors have similar values as the TMS9918A), 0.53 and 0.8 (the maximum luminance figure seen in the TMS9928A datasheet). Thank you, Benjamin "Ben" Edge