The TI-83 Plus (and TI-84 Plus) can be found with one of four different LCD driver ICs, depending on the age of the calculator and its manufacturer. These are accessed by ports 10 and 11.
The original Toshiba T6A04 is found on TI-83 Plus prototypes, in addition to the non-Parcus TI-82 and TI-83s. It may also appear on early production TI-83 Pluses from Inventec. It has a 120x64 pixel video RAM.
TI-83 Pluses from Inventec before 2004 (changed in hardware revision S-'E'), and TI-83 Pluses from Nam Tai before 2007, use the Toshiba T6A04A. It has a 120x64 pixel video RAM, and is externally identical to the T6A04. TI-82 and TI-83 Parcus calculators can also have this LCD driver.
The Toshiba T6K04 is found in Inventec calculators manufactured after 2004 (changed in hardware revision S-'E'), uses both a smaller package and a smaller external component count compared to its T6A04A predecessor, and can operate at 3.3V in addition to 5V. All TI-84 Plus series calculators prior to the Novatek switch use the T6K04. It has a 128x64 pixel video RAM (command $3F maps to a valid column).
In 2007, all manufacturers switched to the Novatek NT7564H. Unlike the Toshiba chips, it only has a 96x64 pixel video RAM, so there is no 'extra' video RAM. These LCD drivers process instructions much faster than the Toshiba drivers, and need a LCD busy delay of only a few clock cycles on a TI-84 Plus. No datasheet appears to be available.
New Kinpo LCD Driver
These behave similarly to the NT7564H, except that reading the status port can scramble the contents of the internal video RAM pointer. The switch from the NT7564H to this new LCD driver happened during 2018, while production of the grayscale calculators was exclusively under Kinpo Philippines.
- On the TI-83 Plus, this corresponds with factory 'L', hardware revisions 'D' and newer.
- On the TI-84 Plus, this corresponds with factory 'L', hardware revisions 'AC' and newer.
Exact hardware revision boundaries are still being determined at the time of this article being written, but they are narrowed down to +/- one hardware revision.
The LCD driver IC itself is actually situated on the LCD itself, bonded to the top of the LCD panel by gray silicone. The chip is about 1mm x 4mm. All support circuitry is on the calculator's mainboard.
Testing for the new LCD driver
Write a known pattern of unique bytes to a column of the LCD, checking if the LCD is busy by reading the status port (10) after every write. Read the video RAM of that column back, and see if the pattern matches. If it matches, it probably isn't the new driver. I (CVSoft) write the column three times, as there's a possibility that an entire column can get written successfully. Failure appears to depend on what's on the bus, as it's very unpredictable.
Avoiding issues with the new LCD driver
See the documentation for TI-83 Plus Port 10.