For now, i only retrace an Epoch TV Vader. They are many pins not connected (almost 50%) and i haven't tried those on an oscilloscope to see what's they are doing (or not). The chip called the C626C, done also by NEC, is an 18-pins TV Video Modulator which takes some outputs of the D774C and modulates it with an RF output to either Channel 1 or 2.
But...this C626C is in fact a clone of the National Semiconductor LM1889N! The only difference is that the C626C only needs 6-9 Volts instead of 12-15 Volts like on the LM1889. So here's the pinout of the uPD774C:
Since the C626C is like the LM1889, you could convert with ease to an Audio/CompositeVideo output (Sound is pin #19) or even S-Video (Y and C or Luma and Chroma) or if you dare try but the result would be awesome (yup...big pixels on screen...not the movie mind you...lol!) is to output to R-Y, B-Y and Chroma+Luma (aka Component Video) but you would need to amplify those outputs because those signals are too weak to be displayed.
I haven't checked all the other Epoch Cassette Vision cartridges i have (i'm only missing #11 and 12) if the pinouts would match or not. At least, this is a step in the right direction for future emulation.
UPDATE: Since i was missing two pins to be identified, that was bugging me so i decided after i posted this, to finish the pinouts and i'm very glad that i did because i completely screwed-up the pinouts by inverting them (42 was 1 and so forth). So this is the correct pinouts of the D774C with also the missing sound pin, and if you need the CLOCK frequency, it is 3,58MHz. Now i need to send this to plgDavid pronto!
--- Sly DC ---