Just to give some information if someone wants to get the screenshot: tech note 94 is actually quite good on that point, and is the first reference to go to.
The only information that's missing is how the graphic data itself is organized, and it's done quite logically: the screen size is 240*64. The pixels are coded in binary more (each pixel is on or off), and by groups of 4. The groups come in order from left to right, top to bottom (first line, then second line, etc.) And each group of 4 pixels comes as a number between 0 and 15, simple binary code (0 is 0 0 0 0, 4 dark pixels, 15 is 1 1 1 1, four bright pixels, e is 1 1 1 0).
All the best.
