Screen layout

As we know, the jupiter ACE screen is a character based layout. Effectively, each character on the 32x24 layout is a pointer to the character RAM with pixel rows that define the graphic of the character.

An interesting thing to note, is that the Character RAM only has room for 128 characters. The highest bit (7) indicates whether the character is to be rendered in reverse video, or not.

Test rendering

Here is an image of the software that will run on the Raspberry PI Zero, attached to the MillRACE Video module.

Each character is defined as a block  of rows in incremental values from 0 to 0x7F. And the screen RAM is filled in a 0-0xFF cycle.

The rendering is the easy bit ... now I need to read the data from the real RAM!