Version analysis of RES2 - Elite on the BBC Micro and NES

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

Cassette, Disc (flight), Disc (docked), 6502 Second Processor, Master and Electron

Code variations between these versions are shown below.

       Name: RES2
       Type: Subroutine
   Category: Start and end
    Summary: Reset a number of flight variables and workspaces


 This is called after we launch from a space station, arrive in a new system
 after hyperspace, launch an escape pod, or die a cold, lonely death in the
 depths of space.


 Returns:

   Y                    Y is set to &FF


.RES2

Code variation 1 of 15A variation in the comments only

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

Master
\JSR stopbd             \ This instruction is commented out in the original
                        \ source

Code variation 2 of 15Related to the Electron version

The Electron version has a hard-coded number of stardust particles on-screen, so there is no need to reset it after launch from the station.

This variation is blank in the Master and Electron versions.

Cassette, Flight, Docked, 6502SP
 LDA #NOST              \ Reset NOSTM, the number of stardust particles, to the
 STA NOSTM              \ maximum allowed (18)

 LDX #&FF               \ Reset LSX2 and LSY2, the ball line heaps used by the
 STX LSX2               \ BLINE routine for drawing circles, to &FF, to set the
 STX LSY2               \ heap to empty

 STX MSTG               \ Reset MSTG, the missile target, to &FF (no target)

Code variation 3 of 15Specific to an individual platform

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

Cassette, Docked, 6502SP, Master, Electron
Flight
 LDA #128               \ Set the current pitch rate to the mid-point, 128
 STA JSTY

 STA ALP2               \ Reset ALP2 (roll sign) and BET2 (pitch sign)
 STA BET2               \ to negative, i.e. pitch and roll negative
 LDA #128               \ Set the current pitch and roll rates to the mid-point,
 STA JSTX               \ 128
 STA JSTY

 ASL A                  \ This sets A to 0

Code variation 4 of 15Specific to an individual platform

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

6502SP, Master
 STA BETA               \ Reset BETA (pitch angle alpha) to 0

 STA BET1               \ Reset BET1 (magnitude of the pitch angle) to 0

Code variation 5 of 15Specific to an individual platform

This variation is blank in the Disc (flight) version.

Cassette, Docked, 6502SP, Master, Electron
 STA ALP2+1             \ Reset ALP2+1 (flipped roll sign) and BET2+1 (flipped
 STA BET2+1             \ pitch sign) to positive, i.e. pitch and roll negative

 STA MCNT               \ Reset MCNT (the main loop counter) to 0

Code variation 6 of 15A variation in the comments only

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

Master
\STA TRIBCT             \ This instruction is commented out in the original
                        \ source

Code variation 7 of 15Specific to an individual platform

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

Flight
 STA QQ22+1             \ Set the on-screen hyperspace counter to 0

Code variation 8 of 15A variation in the labels only

This variation is blank in the Cassette, Disc (flight), 6502 Second Processor, Master and Electron versions.

Docked
.modify

 LDA #3                 \ Reset DELTA (speed) to 3
 STA DELTA

Code variation 9 of 15Specific to an individual platform

This variation is blank in the Disc (flight) version.

Cassette, Docked, 6502SP, Master, Electron
 STA ALPHA              \ Reset ALPHA (roll angle alpha) to 3

 STA ALP1               \ Reset ALP1 (magnitude of roll angle alpha) to 3

Code variation 10 of 15Specific to an individual platform

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

Master
\LDA #&10               \ These instructions are commented out in the original
\STA COL2               \ source

 LDA #0                 \ Set dontclip to 0 (though this variable is never used,
 STA dontclip           \ so this has no effect)

 LDA #191               \ Set Yx2M1 to 191, the number of pixel lines in the
 STA Yx2M1              \ space view

Code variation 11 of 15Specific to an individual platform

This variation is blank in the Disc (docked) version.

Cassette, Flight, 6502SP, Master, Electron
 LDA SSPR               \ Fetch the "space station present" flag, and if we are
 BEQ P%+5               \ not inside the safe zone, skip the next instruction

 JSR SPBLB              \ Light up the space station bulb on the dashboard

 LDA ECMA               \ Fetch the E.C.M. status flag, and if E.C.M. is off,
 BEQ yu                 \ skip the next instruction

 JSR ECMOF              \ Turn off the E.C.M. sound

.yu

 JSR WPSHPS             \ Wipe all ships from the scanner

Code variation 12 of 15A variation in the comments only

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

Cassette, Flight, Docked, Electron
6502SP, Master
 JSR ZERO               \ Zero-fill pages &9, &A, &B, &C and &D, which clears
                        \ the ship data blocks, the ship line heap, the ship
                        \ slots for the local bubble of universe, and various
                        \ flight and ship status variables
 JSR ZERO               \ Reset the ship slots for the local bubble of universe,
                        \ and various flight and ship status variables

Code variation 13 of 15Minor and very low-impact

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

Cassette, Electron
Flight, Docked, 6502SP, Master
 LDA #LO(WP-1)          \ We have reset the ship line heap, so we now point
 STA SLSP               \ SLSP to the byte before the WP workspace to indicate
 LDA #HI(WP-1)          \ that the heap is empty
 STA SLSP+1
 LDA #LO(LS%)           \ We have reset the ship line heap, so we now point
 STA SLSP               \ SLSP to LS% (the byte below the ship blueprints at D%)
 LDA #HI(LS%)           \ to indicate that the heap is empty
 STA SLSP+1

Code variation 14 of 15Specific to an individual platform

This variation is blank in the Master version.

Cassette, Flight, Docked, 6502SP, Electron
 JSR DIALS              \ Update the dashboard

Code variation 15 of 15Specific to an individual platform

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

Flight
 JSR U%                 \ Call U% to clear the key logger

                        \ Finally, fall through into ZINF to reset the INWK
                        \ ship workspace