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Elite on the BBC Micro

Dashboard: BULB (Cassette version)

Name: BULB [View in context] Type: Subroutine [Compare versions] Category: Dashboard Summary: Draw an indicator bulb on the dashboard
Arguments: A The y-coordinate of the bulb as a low-byte screen address offset within screen page &7D (as both bulbs are on this character row in the dashboard) (Y X) The address of the character definition of the bulb to be drawn (i.e. ECBT for the E.C.M. bulb, or SPBT for the space station bulb)
.BULB STA SC \ Store the low byte of the screen address in SC STX P+1 \ Set P(2 1) = (Y X) STY P+2 LDA #&7D \ Set A to the high byte of the screen address, which is \ &7D as the bulbs are both in the character row from \ &7D00 to &7DFF JMP RREN \ Call RREN to print the character definition pointed to \ by P(2 1) at the screen address pointed to by (A SC), \ returning from the subroutine using a tail call