Here's how the N64's video works. The video is generated by the
Reality Co-Processor and clocked into the DAC through a bus 7 bits
wide. This video data consists of four (7 bit) bytes synchronised with
the 50Mhz Clock signal. There is another signal, I'll call it !DSYNC,
which is active on the first byte of each four byte set.
The problem with the N64 is that it's DAC doesn't output RGB (with the
exception of a few early NTSC consoles with the VDP-NUS DAC), the RGB
video is encoded as Composite and S-video internaly. It is for this
reason that I have created an RGB video DAC: To connect in parallel
with the existing DAC and fulfill this missing function that Nintendo
so carelessly omitted.
My RGB DAC is made from a CPLD (Complex Programmable Logic Device)
which latches the video data and drives an R2R resistor ladder to make
an analog video signal. The analog video is wired to the unused pins on
the A/V port in the same configuration as the SNES.
