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This port only exists on the the TI-84 Plus and the TI-84 Plus Silver Edition. On the standard TI-83 Plus, it acts as a shadow of port 04. On the TI-83 Plus Silver Edition, this port has no effect.


Port Number: 54h

Function: USB Controller Control

This port controls the USB controller. It is closely tied to port 4C


  • Bit 0: Unknown. OS sometimes sets this along with 1, port 81.
  • Bit 1: USB controller power. Reset means powered. Resetting causes a 5.67 mA increase in draw.
  • Bit 2: Setting this also sets 4, port 4C. This along with 3, port port 4C turn the 80-AF ports on. Causes a 1.15 mA increase in draw.
  • Bit 3: Unchangeable
  • Bit 4: Unknown.
  • Bit 5: Unchangeable
  • Bit 6: 5, port 4C is the inverse of this. Must be set to do USB stuff. Causes a 0.22 mA increase in draw.
  • Bit 7: Setting this also sets 6, port 4C. Must be set to do USB stuff.


Under normal conditions, you would output C4h to this port to use USB. When you are done, output 02h or suffer serious battery usage.

If 3, port 3A is set. You should first output 44h to this then follow it with C4h to use USB.