====== AppleTalk Undocumented Functionality ======

Here is some AppleTalk functionality not documented in the APDA //Apple II AppleShare Programmer's Guide//.

===== Init (function $01) ====

The APDA documentation mentions the Init function, then says never to call it and gives no parameter list for it.  Here is its parameter list:

^ Pos ^ Name        ^ Size ^ Value ^
| $00 | Async Flag  | Byte | $00 (Synchronous only) |
| $01 | Command     | Byte | $01 |
| $02 | Result Code | Word | <-  |
| $04 | Init flags  | Byte | See below. |
| $05 | P8 Entry    | Long | P8 MLI entry address |
| $09 | Node number | Byte | Preferred node number or $00 |
| $0A | Unknown     | Word | ? |

Init flags:

^ Value ^ Function ^
| $00   | Partial init, no MLI global page update \\ Used during netboot |
| $80   | Full init, no MLI global page update \\ Used during IIgs boot |
| $40   | Full init, MLI global page update \\ Used by ATINIT and boot block LOGON |

To initialize AppleTalk just enough to do ATP when ProDOS is not loaded, set up an IRQ handler that does ''JSR $Cn19 '' followed by ''RTI'' (where n is the slot number of the Workstation Card) and issue the init call with all parameters 0 except for the command byte of $01, then do ''JSR $Cn14'' in the manner of a ProDOS MLI call to initialize it.  When it returns, enable interrupts.  Example code is in [[projects:netboot_lc|NetBoot LC]].

To initalize AppleTalk for use by ProDOS (in, say, an ATINIT file), you must make the call with init flags = $40 and the P8 entry address as $0000BF00.  After the init call returns success the following must take place:  Use the ProDOS 8 ALLOC_INTERRUPT to allocate an interrupt routine with $Cn19 as the routine address, then update the global page MLI vector to go to $Cn14, and finally, enable interrupts.


===== FIUserPrefix (function $2A) =====

The Reserved byte high bit is a direction indicator and is used by the LOGON program
to set the User Prefix when a user volume is mounted.

Specifically, Logon sets it to $AA, but only the high bit matters.