Dreamcast Programming

The Dreamcast VGA box is a peripheral that can be used instead of the standard video lead. In addition to the RCA Composite and audio connectors, the VGA box has a Super Video (YC) connector, and of course the VGA connector. Additionally, it sports a 2.5mm stereo connector intended for connecting a pair of PC speakers.

Functional overview:

                         VGA / Video selector
                              |
                              v

                              n
                     +------------------+
            SVHS --> |                  | <-- VGA connector
   Composite RCA --> |                  |
  Left audio RCA --> |                  | <-- Stereo line out
 Right audio RCA --> |                  |     for PC speakers
                     +------------------+
                             |  |                  
                             \  /
                              ||
                              ||
                         To Dreamcast

Both the RCA audio and the PC speaker audio connectors are active at all times. However, you'll only get video on either the VGA connector, or the SVHS and Composite connectors, at one time (selected with the switch). This is because the box is not a scan doubler, it actually makes the Dreamcast change it's scanrate beteen 15 and 31 kHz. This is also the reason VGA output doesn't work with all games; the game must be able to cope with both scanrates. (The SVHS and Composite works with all games of course.)

The custom A/V connector on the Dreamcast to which the VGA box connects has the following pinout:

   ______________________________________
  |                                      |
  |1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16|
   \____________________________________/

(Female (sort of) connector viewed from outside of console.)

1 GND

2 Audio Right

3 Audio Left

4 +12V

5 +5V

6 31kHz (VGA) select (active low) (Connected to PORT9 on CPU)

7 RGB select (active low) (Connected to PORT8 on CPU)

8 VGA Vertical sync

9 VGA Horizontal sync

10 VGA Composite sync

11 S/Video Chroma (C)

12 S/Video Luma (Y)

13 Composite Video

14 VGA/SCART Blue

15 VGA/SCART Green

16 VGA/SCART Red

When pin 7 is driven low, the Dreacast will output RGB. If it is left high, you will get Composite Video and Super-Video.

Dreamcast Programming by Marcus Comstedt
Last modified: Mon Mar 27 17:13:33 MEST 2000