83Plus:Ports:00

2005-03-27T03:36:36Z

24.117.98.239:

== Synopsis ==
'''Port Number:''' 00h

This port controls the calculator's serial link port (the standard link port present on the 83+, 83+ SE, 84+ and 84+ SE - do not confuse this with the 84+/84+SE's USB link port).

=== Read Values ===
* Bit 0 and 1: The low 2 bits indicate the state of the link port's two lines. A 1 bit indicates a high line, and a 0 bit indicates a low line. When idle (no transfer in progress, no cable plugged in, etc), both lines are usually high (1). When a cable is connected on both ends, a line reads high if and only if both ends have set the line high. The line will read low if either calculator sets it low.
* Bit 5 and 6: Bits 5 and 6 indicate which lines are pulled low by the calculator (unlike bits 0 and 1 they are not influenced by the other calculator). A 1 bit indicates your calculator is holding the line low. A 0 bit indicates your calculator is not holding the line low. (When both calculators have a 0 bit here, the corresponding line will read 1.) In other words, these bits reflect bits 0 and 1 from the most recent write to this port.
* Bit 2: I have absolutely no idea what this means or does...

=== Write Values ===
* Bit 0 and 1: The low 2 bits indicate what state the lines should be put into. A 1 bit will pull the line low. A 0 bit will stop holding the line low (allowing it to go high if the other calculator is not holding it low).
* Bit 2: I have absolutely no idea what this means or does, except that any change of this bit causes both lines to be released, and writing with this bit set causes bit 2 to read 1, and the next write causes it to read 0 and both lines are released.

== Comments ==
As mentioned bit 2's effect is unknown. An example of it's behavior follows:
<nowiki>Start, read 03.
Write 02, read 01.
Write 07, read 07.
Write 07, read 03.
Write 07, read 07.
Write 00, read 03.
Write 09, read 07.
Write 01, read 03.</nowiki>

Note: Transferring an entire byte requires you to implement some form of protocol. Examples include TI's official linking protocol, and Michael Vincent's TachyonLink protocol (linkies to be available later).

== Example ==
<nowiki>ld a, 0 ;Release both lines.
out (0), a
in a, (0) ;03h
ld a, 2 ;Hold bit 1 low.
out (0), a
in a, (0) ;21h
ld a, 1 ;Relase bit 1, hold bit 0 low.
out (0), a
in a, (0) ;12h
ld a, 3 ;Hold bit 1 low. Bit 0 stays low.
out (0), a
in a, (0) ;30h
ld a, 0 ;Release both lines.
out (0), a</nowiki>

== Credits and Contributions ==
* '''/dev/urandom:''' Because of your randomness, this project is possible.

WikiTI - User contributions [en]

83Plus:Ports:00