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⌂ ∞ Elite on the BBC Micro and NES

Version analysis of FX200

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

Code variations between these versions are shown below.

       Name: FX200
       Type: Subroutine
   Category: Utility routines
    Summary: Set the behaviour of the ESCAPE and BREAK keys



 This is the equivalent of a *FX 200 command, which controls the behaviour of
 the ESCAPE and BREAK keys.



 Arguments:

   X                    Controls the behaviour as follows:

                          * 0 = Enable ESCAPE key
                                Normal BREAK key action

                          * 1 = Disable ESCAPE key
                                Normal BREAK key action

                          * 2 = Enable ESCAPE key
                                Clear memory if the BREAK key is pressed

                          * 3 = Disable ESCAPE key
                                Clear memory if the BREAK key is pressed



.FX200

 LDY #0                 \ Call OSBYTE 200 with Y = 0, so the new value is set to
 LDA #200               \ X, and return from the subroutine using a tail call
 JMP OSBYTE

Code variation 1 of 1Other (e.g. bug fix, optimisation)

There's an extra RTS in the cassette version that is never used, which is only noteworthy because spare bytes are very hard to come by in that version, as it's so heavily optimised for compactness of code.

This variation is blank in the Disc (docked) and 6502 Second Processor versions.

Cassette, Electron
 RTS                    \ This instruction has no effect, as we already returned
                        \ from the subroutine