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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 05.


Port Number: 15h

Function: ASIC Version

This port reports the ASIC version from which the number of RAM pages and USB driver revision can be determined. This works for the TI-83+SE, but not the TI-83+, so first check bit 7 of port 2 before using this to check the HW capabilities. The TI-84+ and TI+84+SE use the exact same ASICs (44h, 45h, 55h); see port 21 for how to check how much flash there is. The TI-84+CSE uses the 45h ASIC. The TI-84+/SE switched to the TA1 ASIC on either production run G or H, which was sometime between late 2006 and early 2007. (The production run is given in the second half of the serial number on the back of a calculator, which has the form X-1234Y. X is the manufacturing plant, 12 is the month, 34 is the year, and Y is the production run.)

Although this page isn't relevant to the TI-83+, I don't know of a better place to put this, so. . . . The TI-83+ models containing discrete Z80s have their Z80s make bits 3 and 5 (the unused bits) of the flags register copies of the results. But, later TI-83+es have their Z80s integrated with the ASIC. They, and the TI-83+SE and TI-84+/C/SE series all have their Z80s always return 0 on those bits. I don't know what this means in terms of what Z80 design is being used---is it a knock-off, or did Zilog just issue a different design for embedded Z80s? Also, what does this mean for the LD A, I/R interrupt-enable-detection bug?

Read Values

  • 33 - TI-REF 83PL2M/TA2 - No USB driver and no on-ASIC RAM; the RAM is in a separate 128 K RAM chip.
  • 44 - TI-REF 83PLUSB/TA2 - Uses old USB driver and has 128KB of RAM
  • 45 - TI-REF 84PLUSB/TA3 - Uses new USB driver and has 128KB of RAM
  • 55 - TI-REF 84PLC/TA1 - Uses new USB driver and has 48KB of RAM

Write Values

No effect


Even though this port is in the protected range, it can't be written to. So there's really no reason to call it protected.