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Elite on the BBC Micro

Version analysis of WPSHPS

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

Code variations between these versions are shown below.

Name: WPSHPS Type: Subroutine Category: Dashboard

Code variation 1 of 6A variation in the comments only

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Cassette, Flight, Docked, 6502SP, Master

Electron

Summary: Clear the scanner, reset the ball line and sun line heaps
Summary: Clear the scanner and reset the ball line heap

Code variation 2 of 6A variation in the comments only

Tap on a version to expand it, and tap it again to show to all variations.

Cassette, Flight, Docked, 6502SP, Master

Electron

Remove all ships from the scanner, reset the sun line heap at LSO, and reset the ball line heap at LSX2 and LSY2.
Remove all ships from the scanner and reset the ball line heap at LSX2 and LSY2.
.WPSHPS LDX #0 \ Set up a counter in X to work our way through all the \ ship slots in FRIN .WSL1 LDA FRIN,X \ Fetch the ship type in slot X BEQ WS2 \ If the slot contains 0 then it is empty and we have \ checked all the slots (as they are always shuffled \ down in the main loop to close up and gaps), so jump \ to WS2 as we are done

Code variation 3 of 6A variation in the comments only

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Cassette, Flight, Docked, 6502SP, Master

Electron

BMI WS1 \ If the slot contains a ship type with bit 7 set, then \ it contains the planet or the sun, so jump down to WS1 \ to skip this slot, as the planet and sun don't appear \ on the scanner
BMI WS1 \ If the slot contains a ship type with bit 7 set, then \ it contains the planet, so jump down to WS1 to skip \ this slot, as the planet don't appear on the scanner

Code variation 4 of 6Specific to an individual platform

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

Cassette, Flight, 6502SP, Master, Electron

STA TYPE \ Store the ship type in TYPE
 JSR GINF               \ Call GINF to get the address of the data block for
                        \ ship slot X and store it in INF

 LDY #31                \ We now want to copy the first 32 bytes from the ship's
                        \ data block into INWK, so set a counter in Y

.WSL2

 LDA (INF),Y            \ Copy the Y-th byte from the data block pointed to by
 STA INWK,Y             \ INF into the Y-th byte of INWK workspace

 DEY                    \ Decrement the counter to point at the next byte

 BPL WSL2               \ Loop back to WSL2 until we have copied all 32 bytes

 STX XSAV               \ Store the ship slot number in XSAV while we call SCAN

Code variation 5 of 6Specific to an individual platform

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

Cassette, Flight, 6502SP, Master, Electron

JSR SCAN \ Call SCAN to plot this ship on the scanner, which will \ remove it as it's plotted with EOR logic
 LDX XSAV               \ Restore the ship slot number from XSAV into X

 LDY #31                \ Clear bits 3, 4 and 6 in the ship's byte #31, which
 LDA (INF),Y            \ stops drawing the ship on-screen (bit 3), hides it
 AND #%10100111         \ from the scanner (bit 4) and stops any lasers firing
 STA (INF),Y            \ at it (bit 6)

.WS1

 INX                    \ Increment X to point to the next ship slot

 BNE WSL1               \ Loop back up to process the next slot (this BNE is
                        \ effectively a JMP as X will never be zero)

.WS2

Code variation 6 of 6Related to Elite's use of the Tube

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Cassette, Flight, Docked, Electron

Master

6502SP

LDX #&FF \ Set LSX2 = LSY2 = &FF to clear the ball line heap STX LSX2 STX LSY2
LDX #0 \ Reset the ball line heap by setting the ball line heap STX LSP \ pointer to 0 DEX \ Set X = &FF STX LSX2 \ Set LSX2 = LSY2 = &FF to clear the ball line heap STX LSY2
STZ LSP \ Reset the ball line heap by setting the ball line heap \ pointer to 0 LDX #&FF \ Set X = &FF (though this appears not to be used)
                        \ Fall through into FLFLLS to reset the LSO block

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