around here, a new blog publish from [Ken Shirriff] is nearly as interesting as a new star trip movie. This time, [Ken] tears apart a 76477 noise impacts chip. This chip was state-of-the-art in 1978 as well as utilized in area Invaders, together with lots of other pinball machines as well as games.
[Ken] started out with a die picture from [Sean Riddle] as well as mapped its functions. Unlike a contemporary noise chip, this produced seems based on networks of connected resistors as well as capacitors. even if you aren’t thinking about the chip, per se, [Ken] describes exactly how the die implements active as well as passive devices, together with some crucial analog style principles like present mirrors (although we are quite sure he got his ideal as well as his left mixed up, or perhaps it was a extremely subtle mirror joke).
Before electronics magazines were full of computer projects, they were full of music synthesis jobs as well as the 76477 is like a crude synthesizer on a chip. It has voltage managed oscillators (VCOs), and produces envelopes with certain assault as well as decay times to produce the seems of interest.
This reminded us a bit of the seems from the a lot more advanced MOS6581. [Ken] has looked inside a great deal of ICs, including at the 2016 Hackaday SuperConference.