How exactly does sound get encoded by a cochlear implant processor? I've been wanting to know more about how sound is processed by a cochlear implant processor, how they are programmed, and how they stimulate the magnets and electrodes inside. 

How do you take pure tones of varying frequencies, noise signals, and complex speech sounds and turn them into a set of organised electrical signals? 

Also, what is meant when people say that cochlear implants can have one channel, two channels, etc? I'm only familiar with mono and stereo channel, but recently I heard that channels refer to the splitting of a single signal into two separate paths. If the signals sound exactly the same in both channels, the result is a mono perception. If there is a difference in signal, the result would be a stereo image. 

With cochlear implants, they can have up to eight channels or more. How do these work, and just out of curiosity, what sampling rate and bit depth, as well as bitrate is the sound presented? Is it in Pulse code modulation? 

I guess the thing to think about is whether the processor, which is digital converts the analogue sound signals of the microphone into a set of signals that somehow need to be reconverted to another form of Analogue that will stimulate an electromagnet that will stimulate a certain number of electrodes for the brain to perceive sound.
There's an excellent non-specialist (science for the public) book on the history of cochlear implant technology:

"I Can Hear You Whisper: An Intimate Journey through the Science of Sound and Language" by Lydia Denworth

which provides a non-technical description of the use of channels in the encoding.