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CharPad 2.8 User Manual - Subchrist Software, 2021.

High-resolution character images.

High-resolution character images are 8x8 pixels in size and use a bit-depth of 1 bit-per-pixel.

They can therefore use two colours...

• Background colour (0-15), defined in the VIC colour register at memory address $d021 (53281). Pixel = "0".

• Foreground colour (0-15), screen-position dependent, defined in the colour-RAM matrix from $d800 (55296). Pixel = "1".

Notes...

In high-resolution character-mode (without using raster tricks), the Commodore 64 can display up to 256 different character images on-screen.

The background colour is the same for all displayed character images.

The colour-RAM matrix (a 40x25 byte array, only the low nybbles are usable) is available from memory address $d800 (55296).

The following formula can be used to determine the memory address for a particular colour-RAM cell...

55296 + (y * 40) + x