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instructions

24 x 156 x 5 TRS-80 Graphics

The TRS-80 Model 3 has just enough CPU time per scan line to change 12 graphics characters. Since each character is 2 pixels wide that gives full control over 24 pixels. After a bit of experimenting I figured that about 5 levels of grayscale was reasonable by alternating different subsets of 12 frames. The code could do a full 24 x 192 display but its pretty memory intensive. The 12 frames will only fit into 48 KB if the vertical resolution is limited to 156.

The following image flips simulate what you'd see on a real TRS-80. The emulator does a better job, of course.

Standing back from your display makes the image look a bit better. Do you recognize the celebrity?


George Phillips, July 5, 2009. gp2000 -at- shaw.ca