Skip to navigation

Elite on the BBC Micro and NES

Dashboard: iff_index

[Elite-A, Loader]

Name: iff_index [Show more] Type: Subroutine Category: Dashboard Summary: Return the type index for this ship in the I.F.F. system Deep dive: The I.F.F. system
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * Elite loader (Part 1 of 3) calls iff_index

This routine is copied to &0D7A in part 1 above. Returns: X The index for the current ship in the I.F.F. system: * 0 = Clean Innocent trader, innocent bounty hunter * 1 = Station tracked Cop, space station, escape pod * 2 = Debris Cargo, alloy plate, asteroid, boulder, splinter * 3 = Missile * 4 = Offender/fugitive Pirate, non-innocent bounty hunter If there is no I.F.F. system fitted, the index returned in X is always 0
\ --- Mod: Code added for Elite-A: --------------------> .iff_index LDX CRGO \ If we do not have an I.F.F. system fitted (i.e. CRGO BEQ iff_not \ is zero), jump to iff_not to return from the routine \ with X = 0 \ If we get here then X = &FF (as CRGO is &FF if we have \ an I.F.F. system fitted) LDY #36 \ Set A to byte #36 of the ship's blueprint, i.e. the LDA (INF),Y \ NEWB flags ASL A \ If bit 6 is set, i.e. this is a cop, a space station ASL A \ or an escape pod, jump to iff_cop to return X = 1 BCS iff_cop ASL A \ If bit 5 is set, i.e. this is an innocent bystander BCS iff_trade \ (which applies to traders and some bounty hunters), \ jump to iff_trade to return X = 0 LDY TYPE \ Set Y to the ship's type - 1 DEY BEQ iff_missle \ If Y = 0, i.e. this is a missile, then jump to \ iff_missle to return X = 3 CPY #8 \ If Y < 8, i.e. this is a cargo canister, alloy plate, BCC iff_aster \ boulder, asteroid or splinter, then jump to iff_aster \ to return X = 2 \ If we get here then the ship is not the following: \ \ * A cop/station/escape pod \ * An innocent bystander/trader/good bounty hunter \ * A missile \ * Cargo or an asteroid \ \ So it must be a pirate or a non-innocent bounty hunter INX \ X is &FF at this point, so this INX sets X = 0, and we \ then fall through into the four INX instructions below \ to return X = 4 .iff_missle INX \ If we jump to this point, then return X = 3 .iff_aster INX \ If we jump to this point, then return X = 2 .iff_cop INX \ If we jump to this point, then return X = 1 .iff_trade INX \ If we jump to this point, then return X = 0 .iff_not RTS \ Return from the subroutine \ --- End of added code -------------------------------> COPYBLOCK iff_index, P%, iff_index_code ORG iff_index_code + P% - iff_index