As the term Application-Specific implies, the chip is only manufactured for TI's graphing calculators. They don't publish a data sheet. Kerm is the best bet for that kind of information. I may, in the next few weeks, be able to provide micrographs of the ASIC, but that's a long way from a pinout.
The TI-84+ and the TI-84+SE appear to use exactly the same ASIC; only the actual flash chip differs. Be aware that there are at least three known revisions of the ASIC, whose pinouts may all be quite different.