README.txt
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FCB - Flexible Color Bitmap
by Daniel Kahlin (tlr) <daniel@kahlin.net>
2008-11-22

SOURCE FORMAT SUGGESTION
  - one layer for background   (0-15)
  - one layer for aux color    (0-15)
  - one layer for border color (0-7)
  - one layer for color mem    (0-7)
  - one layer for pixel data hires (color mem)
  - one layer for pixel data MC01 (color mem)
  - one layer for pixel data MC10 (border color)
  - one layer for pixel data MC11 (aux color)

  the layers have 24 pixels border on all edges which is clipped.


PARAMETERS
- bitmapped mode
- 21 * 48 chars, 168 * 192 hires pixels
- Each char can be either 8*4 pixels (hires) or 4*4 pixels (multicolor)
- Hires chars have:
  - one char color per char (0-7)
  - one cpu controlled background color (0-15)
- Multicolor chars have in addition to this:
  - one cpu controlled aux color (0-15)
  - one cpu controlled border color (0-7)

- cpu control:
  - border and background color share the same register ($900F)
  - aux color is separate ($900E)  (shared with volume)
  - each line starts with a fresh $900E and $900F value.
  - one of $900E and $900F can change at several points during the line
  - the nominal change time for one register is 24 pixels.
  - counting from the start of the line one change can be 16 or 20 pixels wide.
  - if a 32 pixel or larger change occur an additional 16 or 20 pixel change can follow.
  - the start of the whole line can be changed in steps of 4 pixels.
  - colors are changed one hires pixel late with respect to char boundaries.  (which means 0.5 multicolor pixel)
  - multicolor border color is the same as the actual border color which requires
    it to be equal to the border color at X=0 and X=167 otherwise there will be border defects.

