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F18A programming, info, and resources

f18a fpga vdp 9918a 9928 video hardware mods upgrade updates

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#576 matthew180 ONLINE  

matthew180

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Posted Thu May 11, 2017 3:28 PM

In the original color mode, the pattern pixel ('0' or '1') selects between one of two colors from the color table.  If either color value from the color table is zero, then the backdrop color is used (i.e. the pixel is transparent).  This is why the 9918A has color black as the second color (see pg. 2-17 in the 9918A data sheet), because you need a way to differentiate between transparent and a color.  If you want to use sixteen *colors* without a transparent, then color zero needs to be your black and you need to set the backdrop color (via VR7) to black so that the zero-index transparent pixels show as black.

 

Using the palette above in post #570, just set VR7 to >x0 (the low nibble needs to be 0) and it should work as expected.



#577 InsaneMultitasker OFFLINE  

InsaneMultitasker

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Posted Thu May 11, 2017 7:28 PM


Using the palette above in post #570, just set VR7 to >x0 (the low nibble needs to be 0) and it should work as expected.

Setting VR#7 like you suggested seems to have done the trick.  The palette is working now, and I've been able to test a few routines against it!  The index magic is still a bit of a mystery to me ;)   Thank you and Rasmus for helping me resolve this!



#578 matthew180 ONLINE  

matthew180

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Posted Thu May 11, 2017 8:29 PM

I'll see if I can get something written up that explains the color selection.



#579 timofonic OFFLINE  

timofonic

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Posted Sun Jun 4, 2017 7:47 AM

Are there guides and communities to make non-TI99 users program for F18A?



#580 matthew180 ONLINE  

matthew180

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Posted Sun Jun 4, 2017 2:41 PM

There are some people writing games for the ColecoVision that take advantage of some of the F18A's enhanced features.

 

The F18A itself is not particular to any one system (like the original VDP), and thus programming it is the same no matter what system.  Most of the examples here should apply to any system since they explain how to program the F18A, and not specifically the 99/4A.  If you can program the 9918A on your system of choice, then you can program the F18A and use the info here.  Asking specific questions is typically the best.

 

The 99/4A is probably the strongest community around the F18A, the ColecoVision would be second.  The MSX1 community never really showed any interest in the F18A (I'm not sure why), and I don't know of any MSX1 software that uses its features.

 

There are a few people using the F18A in home-brew systems or other computers, but mostly for the VGA output AFAIK.







Also tagged with one or more of these keywords: f18a, fpga, vdp, 9918a, 9928, video, hardware, mods, upgrade, updates

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