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:

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

Port 0C:

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

Port 0E:

• Seems to be tied with swapping bank $4000. Before swapping pages this port should contain 00, otherwise data read from pages may not be accurate. I have very little info on this port.

Port 0F:

• Seems to be tied with swapping bank $8000. Before swapping pages this port should contain 00, otherwise data read from pages may not be accurate. I have very little info on this port.

Port 21:

• Although used as a hardware detection, this seems to be ram execution protection. See the talk page for info. Talk Page Port 21

Port 25:

• This port also seems to be flash restriction port like 22. Set to 16 by default.

Port 26:

• This port also seems to be flash restriction port like 23. Set to 32 by default.

Port 2D:

• Only bits 0 and 1 can be altered, doesn't seem to do anything.

Port 2E:

• All bits can be altered but only 2 seem to have an effect. This port needs more information.

USB Ports:

• All information about the USB ports are handled here.

Comments

Other ports have unknown functions but are never written to, read from, or change in any way.

There is still quite bit unknown, but most seems to be insignificant.

Credits and Contributions

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