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Universe: ping

[BBC Micro disc version, Flight]

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: * 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