Category:83Plus:Ports:Unknown

Synopsis

There are several ports that have not yet been totally solved. Here is a list of them and what information is available.

83+ & SE Calculator Ports

Port 04: Writing:

• Bit 3: always 0, doesn't seem to have any effect
• Bit 4: always 1, doesn't seem to have any effect, guessing leftover from 83 code
• Bit 5: always 1, guessing same as 83
• Bit 6: default 1, guessing same as 83
• Bit 7: Voltage level at which port 02 bit 0 flips, default 0

SE Calculator Ports Only

Port 0B:

• Tied to the link assist on the SE calculators. Only written to in boot code where it receives B4.

Port 0C:

• Tied to the link assist on the SE calculators. Only written to in boot code where it receives B4.

Port 0E:

• Tied with swapping bank $4000. Before swapping pages this port should contain 00, otherwise data read from those pages may not be accurate.

Port 0F:

• Tied with swapping bank $8000. Before swapping pages this port should contain 00, otherwise data read from those pages may not be accurate.

Port 21:

• Although used as a hardware detection, it's more likely to be ram execution protection. See the talk page for more info. Talk Page Port 21

Port 25:

• This port acts similarly to flash restriction port 22. Set to 16 by default. This is a protected port.

Port 26:

• This port acts similarly to flash restriction port 2223. Set to 32 by default. This is a protected port.

Port 2D:

• Only bits 0 and 1 can be altered, but no effect is apparent.

USB Ports:

• All information concerning the USB ports will be handled here.

Comments

Other ports have unknown functions but are never written to, read from, or change in a significant way. Port 15 on the SE calculators has a value that does seem possible to change, but is not used directly. Other ports likely have no purpose at all.

There is still quite bit unknown about the hardware, however the remainder is less significant to or can not be used by the average coder.

Credits and Contributions

• Tijl Coosemans
• Dan Englender
• James Montelongo
• Michael Vincent