Multi-mode graphics adapter for 8 bit computers using a Cyclone 3 FPGA.
| Mode | Type | Resolution |
|---|---|---|
| 1 | Mono Text | 80x30 |
| 1 | Color Text | 80x30 |
| 2 | Lowres Mono Bitmap | 160x120 |
| 3 | Medres Mono Bitmap | 320x240 |
| 4 | (WIP) Hires Mono Bitmap | 640x480 |
| 5 | Lowres Color Bitmap | 160x120 |
| 6 | (WIP) Medres Color Bitmap | 320x240 |
Mono Text
- Low address is the x position on the screen
- High address is the y position on the screen
- 80 bytes in a row per line
Color Text
- Low address is twice the x position on the screen
- High address is the y position on the screen
- Color (see color) value is sent first on even positions, then characters are sent after on odd positions
Lowres Mono Bitmap
- Each byte represents 8 pixels, which show up on the screen from LSB to MSB
- Low address is x position up to 19
- High address is y position up to 119
Medres Mono Bitmap
- Each byte represents 8 pixels, which show up on the screen from LSB to MSB
- Low address is x position for two lines
- 0-39 show up on even lines, 128-167 show up on odd lines
- High address half the y position up to 119
- Each high address has two lines
Hires Moni Bitmap (WIP)
- (WIP)
Lowres Color Bitmap
- Cross between Lowres Bitmap and Color Text
- Color (see color) value is written first
- 8 pixels, LSB to MSB, are written after.
Medres Color Bitmap (WIP) *Cross bewteen Medres Bitmap and C0olor Text
- Color (see color) value is written first
- 8 pixels, LSB to MSB, are written after.
| Register | Name | Description |
|---|---|---|
| 0 | Mode | Graphics mode. See above. |
| 1 | Data | Data to be written to screen memory. Written immediately |
| 2 | Status | Unused (WIP) |
| 3 | Low Address | Low 8 bits of address. Typically X position |
| 4 | High Address | High 8 bits of address. Typically Y position |
| 5 | Command | Command to be executed. Excecuted immediately. |
| Command | Name | Description |
|---|---|---|
| 0 | No Command | No command |
| 1 | Clear all | Clears all memory. Takes some time (400 us approx) |
| 2 | Clear part | Clears memory from 0 to address in 3,4 (WIP) |
Data written to register 1 is immediately written to screen memory at the address in registers 3 and 4. When writing data, make sure the address is set before you write the data. Commands work the same way with register 5.