Universe: ping

       Name: ping                                                    [Show more]
       Type: Subroutine
   Category: Universe
    Summary: Set the selected system to the current system
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * BR1 (Part 2 of 2) calls ping
             * TT102 calls ping


.ping

 LDX #1                 ; We want to copy the X- and Y-coordinates of the
                        ; current system in (QQ0, QQ1) to the selected system's
                        ; coordinates in (QQ9, QQ10), so set up a counter to
                        ; copy two bytes

.pl1

 LDA QQ0,X              ; Load byte X from the current system in QQ0/QQ1

 STA QQ9,X              ; Store byte X in the selected system in QQ9/QQ10

 DEX                    ; Decrement the loop counter

 BPL pl1                ; Loop back for the next byte to copy

 RTS                    ; Return from the subroutine