Voice Recognition Unit
The Voice Recoginition Unit (VRU) is a microphone for the N64 developed by Ambrella. The VRU prototype was built from parts in Akihabara. The VRU is region locked, and known as the VRS (voice recognition system) in Japan. It was released December 12, 1998 in Japan and November 6, 2000 in North America. In North America, the only game supporting the VRU (and includes and requires it, in fact) is Hey You, Pikachu! In Japan, the game Densha de Go! (meaning "Go by train" in english) supports the VRU as well.
The VRU consists of a microphone covered in a yellow foam ball with a 3.5mm audio jack. The microphone can be clipped onto the N64 controller and clamped around the Controller Pak port. Alternatively, the VRU can he hung from the neck. The VRU is calibrated for higher pitched voices. The VRU plugs into controller port #4 and the cable is 6 feet long.
The VRU unit has 4 tripoint screws and contains the following chips (at this time, only speculation on the purpose of each chip is known):
- NEC d9930g (uPD9930 audio CODEC): Converts analog signals from the mic to digital samples that are forwarded to VRD-NUS, gain settings and some other registers are directly programmable via joybus command 13/0x0D
- VRD-NUS (VRS model) / EVR-NUS (VRU model): Probably a repackaged NEC uPD7701x 16-bit DSP, the pinout of the VRD-NUS matches up very well (explaining why there are so many unused pins) and its capabilities line up with expectation: it has an 8-bit bus connecting to VCI-NUS and a serial interface compatible with uPD9930. If so, there are instruction and data ROMs inside. uPD7701x has a JTAG interface but it isn't well documented so whether it can dump the ROM without decapsulation is unclear.
- VCI-NUS: Controls joybus wire transactions and acts as the host controller for VRD-NUS and uPD9930.