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Port Numbers: 18h-1Fh

Function: MD5 Calculation Ports

These ports access the MD5 calculation hardware present on the SE and 84P calculators. These ports will calculate the FF, GG, HH, and II functions required for MD5 digest generation.

Read Values

  • Port 1Ch: LSB of calculated value
  • Port 1Dh: next byte of calculated value
  • Port 1Eh: next byte of calculated value
  • Port 1Fh: MSB of calculated value

Write Values

  • Port 18h: Sets the MD5 register A value. This is a 32-bit output, output values to the port one byte at a time, LSB first.
  • Port 19h: Sets the B register. 32-bit.
  • Port 1Ah: Sets the C register. 32-bit.
  • Port 1Bh: Sets the D register. 32-bit.
  • Port 1Ch: Sets the X register. 32-bit.
  • Port 1Dh: Sets the AC register. 32-bit.
  • Port 1Eh: Sets the S register. 8-bit.
  • Port 1Fh: Selects whether to compute the FF, GG, HH, or II operation. Set port to 0, 1, 2, or 3 respectively.


This port does not exist on the standard 83 Plus, on which the operations are computed in software. For more information on MD5, see rfc1321.