View source for Category:83Plus:Ports:Unknown

[[Category:83Plus:Ports:By_Address|Unknown Ports]]

== 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:83Plus:Ports:21|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 [[83Plus:OS:84_Plus_USB_Information|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'''