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⌂ ∞ ▽ Elite on the 6502

Version analysis of SFRMIS

This code appears in the following versions (click to see it in the source code):

Code variations between these versions are shown below.

       Name: SFRMIS
       Type: Subroutine
   Category: Tactics
    Summary: Add an enemy missile to our local bubble of universe



 An enemy has fired a missile, so add the missile to our universe if there is
 room, and if there is, make the appropriate warnings and noises.



.SFRMIS

 LDX #MSL               \ Set X to the ship type of a missile, and call SFS1-2
 JSR SFS1-2             \ to add a missile to our universe that has AI (bit 7
                        \ set), is hostile (bit 6 set) and has been launched
                        \ (bit 0 clear); the target slot number is set to 31,
                        \ but this is ignored as the hostile flags means we
                        \ are the target

Code variation 1 of 3A variation in the labels only

This variation is blank in the Master version.

Tap on a block to expand it, and tap it again to revert.

Cassette
Flight, 6502SP
Electron
 BCC NO1                \ The C flag will be set if the call to SFS1-2 was a
                        \ success, so if it's clear, jump to NO1 to return from
                        \ the subroutine (as NO1 contains an RTS)

 BCC KYTB               \ The C flag will be set if the call to SFS1-2 was a
                        \ success, so if it's clear, jump to KYTB to return from
                        \ the subroutine (as KYTB contains an RTS)

 BCC ECMOF-1            \ The C flag will be set if the call to SFS1-2 was a
                        \ success, so if it's clear, jump to ECMOF-1 to return
                        \ from the subroutine (as ECMOF-1 contains an RTS)

Code variation 2 of 3Related to the 6502SP version

If speech is enabled on the Executive version, it will say "Incoming missile" every time the "INCOMING MISSILE,SIR" message flashes on-screen.

This variation is blank in the Cassette, Disc (flight), Master and Electron versions.

6502SP
IF _EXECUTIVE

 LDX #1                 \ Call TALK with X = 1 to say "Incoming missile" using
 JSR TALK               \ the Watford Electronics Beeb Speech Synthesiser (if
                        \ one is fitted and speech has been enabled)

ENDIF

 LDA #120               \ Print recursive token 120 ("INCOMING MISSILE") as an
 JSR MESS               \ in-flight message

Code variation 3 of 3Related to the Master version

The Master version has a unique missile launch sound.

Tap on a block to expand it, and tap it again to revert.

Cassette, Flight, 6502SP, Electron
Master
 LDA #48                \ Call the NOISE routine with A = 48 to make the sound
 BNE NOISE              \ of the missile being launched and return from the
                        \ subroutine using a tail call (this BNE is effectively
                        \ a JMP as A will never be zero)

 LDY #solaun            \ Call the NOISE routine with Y = 8 to make the sound
 JMP NOISE              \ of the missile being launched and return from the
                        \ subroutine using a tail call