I accidentally discovered how to display color on a TI-86 while trying to write a grayscale program many years ago:
I was able to do the same thing on my TI-92+:
Both of these calculators have memory-mapped graphics, & all the programs do is write particular values into the display memory at particular times—there is no port modification going on. (Originally—the current TI-86 version pregenerates the memory contents & then changes the display offset at the appropriate rate, which does involve port modification.)
On the TI-86, each time the program starts, the red & green may be that way or swapped, but they stay in their respective places during an individual run. They flash between color & blank (lighter than the background color at that contrast level). The yellow is a checkerboard of the red & green. The blue is simply the foreground color with the contrast turned up a little.
It does not seem to be possible to have red or green in the same column as any other color, & if they do not take up the entire column, they blend with the rest of the column. This seems to preclude displaying 4-color images in this manner.
Does anyone know if this could damage the LCD? It is a cool demo, but both these calculators are discontinued, so I am disinclined to run it if there is a non-negligible risk of ruining them. (I have run the TI-86 version many times in the past for up to a few minutes at a time without any visible damage yet, but that does not guarantee anything.) I am especially wondering if this is related to the "blue line of death" or "bluescale" that are known to be potentially damaging.
EDIT: I changed the description of the yellow stripe because I located & checked the code & found I had mis-remembered.
I was able to do the same thing on my TI-92+:
Both of these calculators have memory-mapped graphics, & all the programs do is write particular values into the display memory at particular times—there is no port modification going on. (Originally—the current TI-86 version pregenerates the memory contents & then changes the display offset at the appropriate rate, which does involve port modification.)
On the TI-86, each time the program starts, the red & green may be that way or swapped, but they stay in their respective places during an individual run. They flash between color & blank (lighter than the background color at that contrast level). The yellow is a checkerboard of the red & green. The blue is simply the foreground color with the contrast turned up a little.
It does not seem to be possible to have red or green in the same column as any other color, & if they do not take up the entire column, they blend with the rest of the column. This seems to preclude displaying 4-color images in this manner.
Does anyone know if this could damage the LCD? It is a cool demo, but both these calculators are discontinued, so I am disinclined to run it if there is a non-negligible risk of ruining them. (I have run the TI-86 version many times in the past for up to a few minutes at a time without any visible damage yet, but that does not guarantee anything.) I am especially wondering if this is related to the "blue line of death" or "bluescale" that are known to be potentially damaging.
EDIT: I changed the description of the yellow stripe because I located & checked the code & found I had mis-remembered.