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This port only exists as a distinct port on the TI-83 Plus Silver Edition, the TI-84 Plus, and the TI-84 Plus Silver Edition. On the standard TI-83 Plus, it acts as a shadow of port 02.


Port Number: 3Ah

Function: Old USB Flags

This port deals with the old USB driver that was only present in 84+BE/SE hardware revisions (none) and A.

Old hardware

Read Values

  • Bits 0-2 - Used for USB related stuff
  • Bit 3 - Set
  • Bits 4-7 - Unknown

Write Values

  • Bits 0-2 - Used for USB related stuff
  • Bit 3 - No effect
  • Bit 4 - Set after using port 04 to check batteries but then reset
  • Bits 5-6 - Unknown
  • Bit 7 - Set before using port 04 to check batteries

New Hardware

Read Values

  • Bits 0-3 - Reset
  • Bits 4-7 - No significance

Write Values

  • Bits 0-3 - Unchangeable
  • Bits 4-7 - Quirky (no effect)


The purpose of the lower 3 bits is unknown. Someone with a model (none) or A calculator will have to do some testing. If the old USB hardware is present, most of the USB ports work differently.

On the old hardware, port 39h also seems to be tied to the functions of this port.

The upper four bits are quirky and are heavily depend on hardware revision. On at least hardware M, the upper 4 bits are tied to the upper 4 bits of port 39h.

Another way to check for the old USB revision is to check port 15h for the value 44h.