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Elite on the BBC Micro

Text: DOT [6502SP version]

Name: DOT [Show more] Type: Subroutine Category: Text Summary: Draw a dash on the compass by sending a #DOdot command to the I/O processor
Context: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: This subroutine is called as follows: * COMPAS calls DOT

Draw a dash on the compass. Arguments: COMX The screen pixel x-coordinate of the dash COMY The screen pixel y-coordinate of the dash COMC The colour and thickness of the dash: * #WHITE2 = a double-height dash in white, for when the object in the compass is in front of us * #GREEN2 = a single-height dash in green, for when the object in the compass is behind us
.DOT LDA COMY \ Store the y-coordinate of the dash in byte #0 of the STA DOTY1 \ parameter block below LDA COMX \ Store the x-coordinate of the dash in byte #1 of the STA DOTX1 \ parameter block below LDA COMC \ Store the dash colour in byte #2 of the parameter STA DOTCOL \ block below LDX #LO(DOTpars) \ Set (Y X) to point to the parameter block below LDY #HI(DOTpars) LDA #DOdot \ Send a #DODKS4 command to the I/O processor to draw JMP OSWORD \ the dash on-screen, returning from the subroutine \ using a tail call .DOTpars EQUB 5 \ The number of bytes to transmit with this command EQUB 0 \ The number of bytes to receive with this command .DOTX1 EQUB 0 \ The x-coordinate of the dash .DOTY1 EQUB 0 \ The y-coordinate of the dash .DOTCOL EQUB 0 \ The colour of the dash RTS \ End of the parameter block