GET CONTEXT FRAME

 Command:       $AF $09
 Data:          <none>

 This command will return a pointer to the saved context.  This will be
 a pointer to all of the registers that were saved on the stack along
 with some other details.  Returns frame address <$wwxxyyzz>

 The pointer returned is to the following structure:

 STRUCTURE      SAD_FRAME,0
        ; The first three are READ-ONLY...  Mainly used to make it
        ; easier to understand what is going on in the system.
        ULONG   SAD_VBR         ; Current VBR (always 0 on 68000 CPUs)
        ULONG   SAD_AttnFlags   ; ULONG copy of the flags (UPPER WORD==0)
        ULONG   SAD_ExecBase    ; execbase
        ; These fields are the user registers...  The registers are
        ; restored from these fields on exit from SAD...
        ; Note that USP is only valid if SR was *NOT* supervisor...
        ULONG   SAD_USP         ; User stack pointer
        ULONG   SAD_D0          ; User register d0
        ULONG   SAD_D1          ; User register d1
        ULONG   SAD_D2          ; User register d2
        ULONG   SAD_D3          ; User register d3
        ULONG   SAD_D4          ; User register d4
        ULONG   SAD_D5          ; User register d5
        ULONG   SAD_D6          ; User register d6
        ULONG   SAD_D7          ; User register d7
        ULONG   SAD_A0          ; User register a0
        ULONG   SAD_A1          ; User register a1
        ULONG   SAD_A2          ; User register a2
        ULONG   SAD_A3          ; User register a3
        ULONG   SAD_A4          ; User register a4
        ULONG   SAD_A5          ; User register a5
        ULONG   SAD_A6          ; User register a6
        ; This is for SAD internal use...  It is the prompt that
        ; SAD is using...  Changing this will have no effect on SAD.
        ULONG   SAD_PROMPT      ; SAD Prompt Longword...  (internal use)
        ; From here on down is the standard exception frame
        ; The first two entries (SR and PC) are standard on all 680x0 CPUs
        uword      sad_sr          ; status register (part of exception frame)
        ULONG   SAD_PC          ; Return address (part of exception frame)


 Command ACK:   $00 $09
 Command DONE:  $1F $09 $ww $xx $yy $zz