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new datasheets, some vga stuff

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Amber
2024-10-22 10:13:18 -04:00
parent 795283a9ff
commit f7b4a31a6a
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https://hackaday.io/project/164728/logs

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max 256k for upd7220
mak 2mb for upd72020
800x600 is *barely* possible with
32k sram is the largest available in dip with the speed neccesary
blanking area *may* be possible on chip. if not the chip produces the neccesary signals. some external logic
800x600 requires dividing pixel clk by 5 to get 8mhz signal clk
this all assumes 4 bit using memory pages
128k + 32k = 160k
5x 32k sram - a lot of ram
160k is enough for 4 bit color at 640x480
160k is enough for 2 bit color at 800x600
simplest to implement, both are standard vga resolutions
32k + 8k = 40k
1x 32k sram + 1x 8k sram - two diff chips
40k is enough for 1 bit color at 640x480
40k is enough for 4 bit color at 320x240 or 320x200
needs linedoubling for 320x240
needs linedoubling and blank area for 320x200
32k
1x 32k sram - simplest, 1 chip
32k is enough for 1 bit color at 640x400
32k is enough for 4 bit color at 320x200
needs blank area for 640x400
needs linedoubling and blank area for 320x200