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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: 8Ch (LSB), 8Dh (MSB)

Equivalent HDRC port: MGC_O_HDRC_FRAME 0x0C

Function: USB Frame Counter

These ports show the current value of the USB frame counter.

Read Values

  • Port 8C: Bits 0-7 of the frame counter.
  • Port 8D: Bits 8-10 of the frame counter.

Write Values

  • No effect


These two ports indicate the frame counter value used (presumably) in the most recently sent or received start-of-frame packet. (In normal operation, SOFs are sent by the host, once per millisecond, and contain an 11-bit counter value.) These ports can be used for timing, or simply as an indication that USB is working (since the USB controller will not generate SOFs unless a device is connected.)