INCLUDE "1-source-files/main-sources/elite-build-options.asm" _GMA85_NTSC = (_VARIANT = 1) _GMA86_PAL = (_VARIANT = 2) _GMA_RELEASE = (_VARIANT = 1) OR (_VARIANT = 2) _SOURCE_DISK_BUILD = (_VARIANT = 3) _SOURCE_DISK_FILES = (_VARIANT = 4) _SOURCE_DISK = (_VARIANT = 3) OR (_VARIANT = 4)COMMODORE 64 ELITE GAME LOADER SOURCE Commodore 64 Elite was written by Ian Bell and David Braben and is copyright D. Braben and I. Bell 1985 The code in this file is identical to the source disks released on Ian Bell's personal website at http://www.elitehomepage.org/ (it's just been reformatted to be more readable) The commentary is copyright Mark Moxon, and any misunderstandings or mistakes in the documentation are entirely my fault The terminology and notations used in this commentary are explained at https://elite.bbcelite.com/terminology The deep dive articles referred to in this commentary can be found at https://elite.bbcelite.com/deep_dives
This source file contains the game loader for Commodore 64 Elite, which itself gets loaded by the disk loader.
This source file produces the following binary file: * COMLOD.unprot.bin after reading in the following files: * LODATA.bin * SHIPS.bin * CODIALS.bin * SPRITE.bin * DATE4.binCODE% = $4000 ; The address where the code will be run LOAD% = $4000 ; The address where the code will be loaded KEY3 = $8E ; The seed for decrypting COMLOD from U% to V%, which is ; the second block of data, after the decryption routine ; ; [Show more]Configuration variables; ; This variable is used by the following: ; ; * Elite loader (Part 1 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveKEY4 = $6C ; The seed for decrypting COMLOD from W% to X%, which is ; the first block of data, before the decryption routine ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 1 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveL1 = $0001 ; The 6510 input/output port register, which we can use ; to configure the Commodore 64 memory layout (see page ; 260 of the Programmer's Reference Guide) ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 2 of 7) ; * Elite loader (Part 3 of 7) ; * Elite loader (Part 7 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveSCBASE = $4000 ; The address of the screen bitmap ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 5 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveIF _GMA_RELEASE DSTORE% = SCBASE + $AF90 ; The address of a copy of the dashboard bitmap, ; which gets copied into screen memory when ; setting up a new screen ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 7 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveSPRITELOC% = SCBASE + $2800 ; The address where the sprite bitmaps get ; copied to during the loading process ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 7 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveELIF _SOURCE_DISK DSTORE% = SCBASE + $2800 ; The address of a copy of the dashboard bitmap, ; which gets copied into screen memory when ; setting up a new screen ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 7 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveSPRITELOC% = SCBASE + $3100 ; The address where the sprite bitmaps get ; copied to during the loading process ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 7 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveENDIF SPOFF% = (SPRITELOC% - SCBASE) / 64 ; Sprite pointers are defined as the ; offset from the start of the VIC-II ; screen bank to start of the sprite ; definitions, divided by 64, so SPOFF% ; is the offset for the first sprite ; definition at SPRITELOC% ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 7 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveD% = $D000 ; The address where the ship data will be loaded ; (i.e. XX21) ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 2 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveVIC = $D000 ; Registers for the VIC-II video controller chip, which ; are memory-mapped to the 46 bytes from $D000 to $D02E ; (see page 454 of the Programmer's Reference Guide) ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 4 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveCOLMEM = $D800 ; Colour RAM, which is used (along with screen RAM) to ; define the colour map of the dashboard in multicolour ; bitmap mode ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 6 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveCIA = $DC00 ; Registers for the CIA1 I/O interface chip, which ; are memory-mapped to the 16 bytes from $DC00 to $DC0F ; (see page 428 of the Programmer's Reference Guide) ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 3 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveCIA2 = $DD00 ; Registers for the CIA2 I/O interface chip, which ; are memory-mapped to the 16 bytes from $DD00 to $DD0F ; (see page 428 of the Programmer's Reference Guide) ; ; [Show more]; ; This variable is used by the following: ; ; * Elite loader (Part 3 of 7) ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveORG $0018 .ZP SKIP 2 ; Stores addresses used for moving content around ; ; [Show more]Name: ZP [Show more] Type: Workspace Address: $0018 to $001B Category: Workspaces Summary: Important variables used by the loaderContext: See this workspace on its own page References: This workspace is used as follows: * DEEORS uses ZP * Elite loader (Part 2 of 7) uses ZP * Elite loader (Part 5 of 7) uses ZP * Elite loader (Part 6 of 7) uses ZP * Elite loader (Part 7 of 7) uses ZP * mvblock uses ZP * mvsm uses ZP; ; This variable is used by the following: ; ; * DEEORS ; * Elite loader (Part 2 of 7) ; * Elite loader (Part 5 of 7) ; * Elite loader (Part 6 of 7) ; * Elite loader (Part 7 of 7) ; * mvblock ; * mvsm ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned above.ZP2 SKIP 2 ; Stores addresses used for moving content around ; ; [Show more]; ; This variable is used by the following: ; ; * DEEORS ; * Elite loader (Part 2 of 7) ; * Elite loader (Part 5 of 7) ; * Elite loader (Part 6 of 7) ; * Elite loader (Part 7 of 7) ; * mvblock ; * mvsm ; ; This list only includes code that refers to the ; variable by name; there may be other references to ; this memory location that don't use this label, and ; these will not be mentioned aboveORG CODE%ELITE LOADER.W% SKIP 0Name: W% [Show more] Type: Variable Category: Utility routines Summary: Denotes the start of the first block of loader code, as used in the encryption/decryption processContext: See this variable on its own page References: This variable is used as follows: * Elite loader (Part 1 of 7) uses W%.LODATA INCBIN "3-assembled-output/LODATA.bin"Name: LODATA [Show more] Type: Subroutine Category: Loader Summary: The binaries for recursive tokens and the game fontContext: See this subroutine on its own page References: This subroutine is called as follows: * Elite loader (Part 2 of 7) calls LODATA.SHIPS INCBIN "3-assembled-output/SHIPS.bin" IF _GMA_RELEASE EQUB $1F, $3F ; These bytes appear to be unused and just contain EQUB $58 ; random workspace noise left over from the BBC Micro ; assembly process ELIF _SOURCE_DISK_BUILD EQUB $B3, $1F, $3F, $58, $98, $A0, $40, $20 ; These bytes appear to be EQUB $1F, $F0, $8C, $98, $1A, $46, $10, $8C ; unused and just contain random EQUB $CF, $3C, $B2, $CF, $C2, $7D, $FF, $2A ; workspace noise left over from EQUB $92, $AB, $A8, $BD, $3E, $85, $9E, $19 ; the BBC Micro assembly process EQUB $85, $F5, $3A, $EF, $06, $E6, $E4, $04 EQUB $07, $E7, $E5, $EA, $AA, $2E, $98, $2F EQUB $10, $F0, $E2, $02, $12, $F2, $E3, $03 EQUB $DA, $BA, $E4, $04, $DB, $BB, $E5, $19 EQUB $39, $85, $25, $2E, $98, $3A, $BB, $B0 EQUB $12, $13, $03, $E3, $F3, $F2, $E2, $7D EQUB $1A, $B2, $5D, $02, $E2, $F0, $10, $03 EQUB $E3, $F2, $8D, $1A, $B2, $40, $78, $2F EQUB $E4, $01, $2C, $ED, $E3, $21, $2B, $5C EQUB $52, $22, $A8, $CB, $07, $2E, $DB, $BB EQUB $E5, $05, $DC, $BC ELIF _SOURCE_DISK_FILES EQUB $38, $E0, $60, $3F, $0F, $7C, $24, $B2 ; These bytes appear to be EQUB $60, $56, $9C, $67, $23, $FA, $81, $91 ; unused and just contain random EQUB $3F, $7C, $29, $BC, $3D, $53, $65, $FB ; workspace noise left over from EQUB $C3, $23, $B7, $9E, $7A, $2F, $29, $F5 ; the BBC Micro assembly process EQUB $EC, $CA, $E8, $0B, $EE, $CC, $CF, $94 EQUB $D8, $C6, $C7, $3F, $00, $D2, $E4, $14 EQUB $04, $D5, $E6, $DD, $94, $9E, $E8, $DF EQUB $96, $A0, $FE, $52, $BE, $AA, $53, $C6 EQUB $D2, $F5, $6B, $C2, $25, $16, $E6, $D6 EQUB $E5, $D4, $5F, $A3, $E5, $1D, $60, $E4 EQUB $D2, $00, $13, $E6, $D5, $7F, $B3, $E5 EQUB $00, $B9, $A7, $13, $E5, $2D, $19, $D0 EQUB $04, $4C, $87, $AE, $74, $CA, $73, $D2 EQUB $35, $09, $96, $A0, $EA, $E1, $98, $A2 EQUB $66, $AE, $C6, $04 ENDIFName: SHIPS [Show more] Type: Subroutine Category: Loader Summary: The binaries for the ship blueprintsContext: See this subroutine on its own page References: This subroutine is called as follows: * Elite loader (Part 2 of 7) calls SHIPS.X% JMP $0185 ; This code is never run, but it was presumably added ; to the code to act as a red herring to confuse any ; crackers exploring the loader codeName: X% [Show more] Type: Variable Category: Utility routines Summary: Denotes the end of the first block of loader code, as used in the encryption/decryption processContext: See this variable on its own page References: This variable is used as follows: * Elite loader (Part 1 of 7) uses X%.FRIN JSR $0134 ; This code is never run (it is overwritten when the ; FRIN variable is used), but it was presumably added ; to the code to act as a red herring to confuse any ; crackers exploring the loader codeName: FRIN [Show more] Type: Variable Category: Loader Summary: A temporary variable that's used for storing addressesContext: See this variable on its own page References: This variable is used as follows: * DEEORS uses FRIN * Elite loader (Part 1 of 7) uses FRIN.ENTRY CLD ; Clear the decimal flag, so we're not in decimal mode LDA #LO(U%-1) ; Set FRIN(1 0) = U%-1 as the low address of the STA FRIN ; decryption block, so we decrypt the loader routine LDA #HI(U%-1) ; at U% below STA FRIN+1 LDA #HI(V%-1) ; Set (A Y) to V% as the high address of the decryption LDY #LO(V%-1) ; block, so we decrypt to V% at the end of the loader ; routine LDX #KEY3 ; Set X = KEY3 as the decryption seed (the value used to ; encrypt the code, which is done in elite-checksum.py) IF _REMOVE_CHECKSUMS NOP ; If we have disabled checksums, skip the call to DEEORS NOP NOP ELSE JSR DEEORS ; Call DEEORS to decrypt between U% and V% ENDIF LDA #LO(W%-1) ; Set FRIN(1 0) = W%-1 as the low address of the STA FRIN ; decryption block, so we decrypt the game data at LDA #HI(W%-1) ; at W% above STA FRIN+1 LDA #HI(X%-1) ; Set (A Y) to X% as the high address of the decryption LDY #LO(X%-1) ; block, so we decrypt to X% at the end of the game data LDX #KEY4 ; Set X = KEY4 as the decryption seed (the value used to ; encrypt the code, which is done in elite-checksum.py) IF _REMOVE_CHECKSUMS NOP ; If we have disabled checksums, skip the call to DEEORS NOP NOP ELSE JSR DEEORS ; Call DEEORS to decrypt between W% and X% ENDIF JMP U% ; Now that both the game data and the loader routine ; have been decrypted, jump to the loader routine at U% ; to load the gameName: Elite loader (Part 1 of 7) [Show more] Type: Subroutine Category: Loader Summary: Unscramble the loader code and game dataContext: See this subroutine on its own page References: No direct references to this subroutine in this source file.DEEORS STX ZP2 ; Store the decryption seed in ZP2 as our starting point STA ZP+1 ; Set ZP(1 0) = (A 0) to point to the start of page A, LDA #0 ; so we can use ZP(1 0) + Y as our pointer to the next STA ZP ; byte to decrypt .DEEORL LDA (ZP),Y ; Set A to the Y-th byte of ZP(1 0) SEC ; Set A = A - ZP2 SBC ZP2 STA (ZP),Y ; Update the Y-th byte of ZP to the new value in A STA ZP2 ; Update ZP2 with the new value in A TYA ; Set A to the current byte index in Y BNE P%+4 ; If A <> 0 then decrement the high byte of ZP(1 0) to DEC ZP+1 ; point to the previous page DEY ; Decrement the byte pointer CPY FRIN ; Loop back to decrypt the next byte, until Y = the low BNE DEEORL ; byte of FRIN(1 0), at which point we have decrypted a ; whole page LDA ZP+1 ; Check whether ZP(1 0) matches FRIN(1 0) and loop back CMP FRIN+1 ; to decrypt the next byte until it does, at which point BNE DEEORL ; we have decrypted the whole block RTS ; Return from the subroutineName: DEEORS [Show more] Type: Subroutine Category: Loader Summary: Decrypt a multi-page block of memoryContext: See this subroutine on its own page References: This subroutine is called as follows: * Elite loader (Part 1 of 7) calls DEEORS
Arguments: FRIN(1 0) The start address of the block to decrypt (A Y) The end address of the block to decrypt X The decryption seed.U% LDX #$16 ; Set X = $16 so we copy 22 pages of data from LODATA ; into $0700 to $1CFF LDA #0 ; Set ZP(1 0) = $0700 STA ZP LDA #$7 STA ZP+1 LDA #LO(LODATA) ; Set (A ZP2) = LODATA STA ZP2 LDA #HI(LODATA) JSR mvblock ; Call mvblock to copy 22 pages of data from LODATA to ; $0700, so this copies the following data: ; ; * QQ18 to $0700, the text token table ; ; * SNE to $0AC0, the sine lookup table ; ; * ACT to $0AE0, the arctan lookup table ; ; * FONT to $0B00, the game's text font ; ; * TKN1 to $0E00, the extended token table ; ; The data at TKN1 ends at $1CFF SEI ; Disable interrupts while we set the 6510 input/output ; port register and configure the VIC-II chip LDA L1 ; Set bits 0 to 2 of the 6510 port register at location AND #%11111000 ; L1 to %100 to set the input/output port to the ORA #%00000100 ; following: STA L1 ; ; * LORAM = 0 ; * HIRAM = 0 ; * CHAREN = 1 ; ; and return from the subroutine using a tail call ; ; This sets the entire 64K memory map to RAM ; ; See the memory map at the top of page 265 in the ; Programmer's Reference Guide IF _GMA_RELEASE LDX #$29 ; Set X = $29 so we copy 41 pages of data from SHIPS ; into D% ($D000 to $F8FF) ; ; It isn't necessary to copy this number of pages, as ; the ship data only takes up 32 pages of memory, and ; the extra data that's copied from $F000 to $F8FF is ; just ignored ELIF _SOURCE_DISK LDX #$20 ; Set X = $20 so we copy 32 pages of data from SHIPS ; to D% ($D000 to $EFFF) ENDIF LDA #LO(D%) ; Set ZP(1 0) = D% = $D000 STA ZP LDA #HI(D%) STA ZP+1 LDA #LO(SHIPS) ; Set (A ZP2) = SHIPS STA ZP2 LDA #HI(SHIPS) JSR mvblock ; Call mvblock to copy X pages of data from SHIPS to D% ; ($D000), so this copies the following data: ; ; * XX21 to $D000, the ship blueprints ; ; The data at XX21 ends at $EF8CName: Elite loader (Part 2 of 7) [Show more] Type: Subroutine Category: Loader Summary: Copy the game data to their correct locationsContext: See this subroutine on its own page References: No direct references to this subroutine in this source fileLDA L1 ; Set bits 0 to 2 of the 6510 port register at location AND #%11111000 ; L1 to %101 to set the input/output port to the ORA #%00000101 ; following: STA L1 ; ; * LORAM = 1 ; * HIRAM = 0 ; * CHAREN = 1 ; ; This sets the entire 64K memory map to RAM except for ; the I/O memory map at $D000-$DFFF, which gets mapped ; to registers in the VIC-II video controller chip, the ; SID sound chip, the two CIA I/O chips, and so on ; ; See the memory map at the top of page 264 in the ; Programmer's Reference Guide LDA CIA2+2 ; Set bits 0-1 of CIA2 port A to the output direction ORA #%00000011 ; so we can write to the VIC-II bank selector, which is STA CIA2+2 ; mapped here (0 means input, 1 means output) LDA CIA2+0 ; Set bits 0-1 of CIA2 port A to configure the VIC-II to AND #%11111100 ; use bank 1 ($4000 to $7FFF) ORA #%00000010 ; STA CIA2+0 ; The bank number is inverted, so setting bits 0-1 to ; %10 actually sets bank %01 LDA #%00000011 ; Set CIA1 register $0D to enable and disable interrupts STA CIA+$D ; as follows: ; ; * Bit 0 set = configure interrupts generated by ; timer A underflow ; ; * Bit 1 set = configure interrupts generated by ; timer B underflow ; ; * Bits 2-4 clear = do not change configuration of ; other interrupts ; ; * Bit 7 clear = disable interrupts whose ; corresponding bits are set ; ; So this disables interrupts that are generated by ; timer A underflow and timer B underflow, while leaving ; other interrupts as they are STA CIA2+$D ; Set CIA2 register $0D to enable and disable interrupts ; as follows: ; ; * Bit 0 set = configure interrupts generated by ; timer A underflow ; ; * Bit 1 set = configure interrupts generated by ; timer B underflow ; ; * Bits 2-4 clear = do not change configuration of ; other interrupts ; ; * Bit 7 clear = disable interrupts whose ; corresponding bits are set ; ; So this disables interrupts that are generated by ; timer A underflow and timer B underflow, while leaving ; other interrupts as they areName: Elite loader (Part 3 of 7) [Show more] Type: Subroutine Category: Loader Summary: Configure the memory layout and the CIA chipsContext: See this subroutine on its own page References: No direct references to this subroutine in this source fileLDA #$81 ; Set VIC register $18 to set the address of screen RAM STA VIC+$18 ; to offset $2000 within the VIC-II bank at $4000 (so ; the screen's colour data is at $6000) LDA #0 ; Set VIC register $20 to set the border colour to the STA VIC+$20 ; colour number in bits 0-3 (i.e. colour 0, black) LDA #0 ; Set VIC register $21 to set the background colour to STA VIC+$21 ; the colour number in bits 0-3 (i.e. colour 0, black) LDA #%00111011 ; Set VIC register $11 to configure the screen control STA VIC+$11 ; register as follows: ; ; * Bits 0-2 = vertical raster scroll of 3 ; ; * Bit 3 set = screen height of 25 rows ; ; * Bit 4 set = enable screen ; ; * Bit 5 set = bitmap mode ; ; * Bit 6 clear = extended background mode off ; ; * Bit 7 = bit 9 of raster line for interrupt LDA #%11000000 ; Set VIC register $11 to configure the screen control STA VIC+$16 ; register as follows: ; ; * Bits 0-2 = horizontal raster scroll of 0 ; ; * Bit 3 clear = screen width of 38 columns ; ; * Bit 4 clear = standard bitmap mode ; ; Bits 6 and 7 don't appear to have any effect, so I'm ; not sure why they are being set LDA #%00000000 ; Clear bits 0 to 7 of VIC register $15 to disable all STA VIC+$15 ; eight sprites LDA #9 ; Set VIC register $29 to set the colour of sprite 2 to STA VIC+$29 ; the colour number in bits 0-3 (i.e. colour 9, brown), ; so this makes Trumble 0 brown LDA #12 ; Set VIC register $2A to set the colour of sprite 3 to STA VIC+$2A ; the colour number in bits 0-3 (i.e. colour 12, grey), ; so this makes Trumble 1 grey LDA #6 ; Set VIC register $2B to set the colour of sprite 4 to STA VIC+$2B ; the colour number in bits 0-3 (i.e. colour 6, blue), ; so this makes Trumble 2 blue LDA #1 ; Set VIC register $2C to set the colour of sprite 5 to STA VIC+$2C ; the colour number in bits 0-3 (i.e. colour 1, white), ; so this makes Trumble 3 white LDA #5 ; Set VIC register $2D to set the colour of sprite 6 to STA VIC+$2D ; the colour number in bits 0-3 (i.e. colour 5, green), ; so this makes Trumble 4 green LDA #9 ; Set VIC register $2E to set the colour of sprite 7 to STA VIC+$2E ; the colour number in bits 0-3 (i.e. colour 9, brown), ; so this makes Trumble 5 brown LDA #8 ; Set VIC register $25 to set sprite extra colour 1 to STA VIC+$25 ; the colour number in bits 0-3 (i.e. colour 8, orange), ; for the explosion sprite LDA #7 ; Set VIC register $26 to set sprite extra colour 2 to STA VIC+$26 ; the colour number in bits 0-3 (i.e. colour 7, yellow), ; for the explosion sprite LDA #%00000000 ; Clear bits 0 to 7 of VIC register $1C to set all seven STA VIC+$1C ; sprites to single colour LDA #%11111111 ; Set bits 0 to 7 of VIC register $17 to set all seven STA VIC+$17 ; sprites to double height STA VIC+$1D ; Set bits 0 to 7 of VIC register $1D to set all seven ; sprites to double width LDA #0 ; Clear bits 0 to 7 of VIC register $10 to zero bit 9 of STA VIC+$10 ; the x-coordinate for all seven sprite LDX #161 ; Position sprite 0 (the laser sights) at pixel LDY #101 ; coordinates (161, 101), in the centre of the space STX VIC+0 ; view STY VIC+1 LDA #18 ; Position sprite 1 (the explosion sprite) at pixel LDY #12 ; coordinates (18, 12) STA VIC+2 STY VIC+3 ASL A ; Position sprite 2 (Trumble 0) at pixel coordinates STA VIC+4 ; (36, 12) STY VIC+5 ASL A ; Position sprite 3 (Trumble 1) at pixel coordinates STA VIC+6 ; (72, 12) STY VIC+7 ASL A ; Position sprite 4 (Trumble 2) at pixel coordinates STA VIC+8 ; (144, 12) STY VIC+9 LDA #14 ; Position sprite 5 (Trumble 3) at pixel coordinates STA VIC+10 ; (14, 12) STY VIC+11 ASL A ; Position sprite 6 (Trumble 4) at pixel coordinates STA VIC+12 ; (28, 12) STY VIC+13 ASL A ; Position sprite 7 (Trumble 5) at pixel coordinates STA VIC+14 ; (56, 12) STY VIC+15 LDA #%00000010 ; Set VIC register $1B to all clear bits apart from bit STA VIC+$1B ; 1, so that: ; ; * Sprite 0 (the laser sights) are drawn in front of ; the screen contents ; ; * Sprite 1 (the explosion sprite) is drawn in behind ; the screen contents ; ; * Sprites 2 to 7 (the Trumble sprites) are drawn in ; front of the screen contents ; ; This ensures that when we change views in-game, the ; BLUEBAND routine will hide any part of the explosion ; sprite that's in the screen border area, as it fills ; the border with colour 1Name: Elite loader (Part 4 of 7) [Show more] Type: Subroutine Category: Loader Summary: Configure the VIC-II for screen memory and sprites Deep dive: The split-screen mode in Commodore 64 Elite Sprite usage in Commodore 64 EliteContext: See this subroutine on its own page References: No direct references to this subroutine in this source file; We start by clearing the screen bitmap from $4000 to ; $5FFF by zeroing this part of memory LDA #0 ; Set the low byte of ZP(1 0) to 0 STA ZP TAY ; Set Y = 0 to act as a byte counter LDX #$40 ; Set X = $40 to use as the high byte of ZP(1 0), so the ; next instruction initialises ZP(1 0) to $4000 .LOOP2 STX ZP+1 ; Set the high byte of ZP(1 0) to X .LOOP1 STA (ZP),Y ; Zero the Y-th byte of ZP(1 0) INY ; Increment the byte counter in Y BNE LOOP1 ; Loop back until we have zeroed a whole page at ZP(1 0) LDX ZP+1 ; Set X to the high byte of ZP(1 0) INX ; Increment X to point to the next page in memory CPX #$60 ; Loop back to zero the next page in memory until we BNE LOOP2 ; have zeroed all the way to $5FFF ; We now reset the two banks of screen RAM from $6000 to ; $63FF and $6400 to $67FF, so we can then populate them ; with colour data for the text view ($6000 to $63FF) ; and the space view ($6400 to $67FF) LDA #$10 ; Set A to the colour byte that we want to fill both ; blocks of screen RAM with, which is $10 to set the ; palette to foreground colour 1 (red) and background ; colour 0 (black) ; At this point, X = $60 from above, which we use as the ; high byte of ZP(1 0), and ZP hasn't changed from zero, ; so the next instruction initialises ZP(1 0) to $6000 .LOOP3 STX ZP+1 ; Set the high byte of ZP(1 0) to X .LOOP4 STA (ZP),Y ; Set the Y-th byte of ZP(1 0) to $10 INY ; Increment the byte counter BNE LOOP4 ; Loop back until we have filled a whole page with the ; red/black palette byte LDX ZP+1 ; Set X to the high byte of ZP(1 0) INX ; Increment X to point to the next page in memory CPX #$68 ; Loop back to zero the next page in memory until we BNE LOOP3 ; have zeroed all the way to $67FF ; Next, we populate screen RAM for the space view ($6400 ; to $67FF), starting with the dashboard in the lower ; part of the screen LDA #LO(SCBASE+$2400+$2D0) ; Set ZP(1 0) to the address within the space STA ZP ; view's screen RAM that corresponds to the LDA #HI(SCBASE+$2400+$2D0) ; dashboard (i.e. offset $2D0 within the screen STA ZP+1 ; RAM at SCBASE + $2400, or $6400) LDA #LO(sdump) ; Set (A ZP2) = sdump STA ZP2 LDA #HI(sdump) JSR mvsm ; Call mvsm to copy 280 bytes of data from sdump to the ; dashboard's screen RAM for the space view, so this ; sets the correct colour data for the dashboard (along ; with the data that we copy into colour RAM in part 6) ;LDX #0 ; These instructions are commented out in the original ; ; source ;.LOOP20 ; ;LDA date,X ;STA SCBASE+$7A0,X ; ;DEX ; ;BNE LOOP20 ; Now we populate screen RAM for the text view ($6000 ; to $63FF) to set the correct colour for the border box ; around the edges of the screen ; ; The screen borders are four character blocks wide on ; each side of the screen (so the 256-pixel wide game ; screen gets shown in the middle of the 320-pixel wide ; screen mode) ; ; The outside three character blocks show nothing and ; are plain black, which we achieve by setting both the ; foreground and background colours to black for these ; character blocks ; ; The innermost of the four character blocks on each ; side is used to draw the border box, with the border ; being right up against the game screen, so for this we ; need a palette of yellow on black, so we can draw the ; border box in yellow LDA #0 ; Set ZP(1 0) = $6000 STA ZP ; LDA #$60 ; So ZP(1 0) points to screen RAM for the text view STA ZP+1 LDX #25 ; The text view is 25 character rows high, so set a row ; counter in X .LOOP10 LDA #$70 ; Set A to the colour byte that we want to apply to the ; border box, which is $70 to set the palette to ; foreground colour 7 (yellow) and background colour 0 ; (black) LDY #36 ; Set the colour data for column 36 (i.e. the right edge STA (ZP),Y ; of the border box) to the yellow/black palette LDY #3 ; Set the colour data for column 3 (i.e. the left edge STA (ZP),Y ; of the border box) to the yellow/black palette ; Next, we set the palette to black on black for the ; outside three character blocks on the left side of the ; screen, so they don't show anything at all DEY ; Set Y = 2 to use as a column counter for the three ; character blocks, so we work our way through columns ; 2, 1 and 0 LDA #$00 ; Set A to the colour byte that we want to apply to the ; outer border area, which is $00 to set the palette to ; foreground colour 0 (black) and background colour 0 ; (black) .frogl STA (ZP),Y ; Set the colour data for column Y to the black/black ; palette DEY ; Decrement the column counter BPL frogl ; Loop back until we have set all three character blocks ; on the left edge of this character row to the ; black/black palette ; And now we set the palette to black on black for the ; outside three character blocks on the right side of ; the screen, so they also show nothing LDY #37 ; Set Y = 2 to use as a column counter for the three ; character blocks, so we work our way through columns ; 37, 38 and 39 STA (ZP),Y ; Set the colour data for column 37 to the black/black ; palette INY ; Set the colour data for column 38 to the black/black STA (ZP),Y ; palette INY ; Set the colour data for column 39 to the black/black STA (ZP),Y ; palette LDA ZP ; Set ZP(1 0) = ZP(1 0) + 40 CLC ; ADC #40 ; So ZP(1 0) points to the next character row in screen STA ZP ; RAM (as there are 40 character blocks on each row) BCC P%+4 INC ZP+1 DEX ; Decrement the row counter in X BNE LOOP10 ; Loop back until we have set the colour data for the ; left and right border box edges in the text view ; Now we populate screen RAM for the text view ($6000 ; to $63FF) to set the correct colour for the border box ; around the edges of the space view LDA #0 ; Set ZP(1 0) = $6400 STA ZP ; LDA #$64 ; So ZP(1 0) points to screen RAM for the space view STA ZP+1 LDX #18 ; The space view is 18 character rows high, so set a row ; counter in X .LOOP11 LDA #$70 ; Set A to the colour byte that we want to apply to the ; border box, which is $70 to set the palette to ; foreground colour 7 (yellow) and background colour 0 ; (black) LDY #36 ; Set the colour data for column 36 (i.e. the right edge STA (ZP),Y ; of the border box) to the yellow/black palette LDY #3 ; Set the colour data for column 3 (i.e. the left edge STA (ZP),Y ; of the border box) to the yellow/black palette ; Next, we set the palette to black on black for the ; outside three character blocks on the left side of the ; screen, so they don't show anything at all DEY ; Set Y = 2 to use as a column counter for the three ; character blocks, so we work our way through columns ; 2, 1 and 0 LDA #$00 ; Set A to the colour byte that we want to apply to the ; outer border area, which is $00 to set the palette to ; foreground colour 0 (black) and background colour 0 ; (black) .newtl STA (ZP),Y ; Set the colour data for column Y to the black/black ; palette DEY ; Decrement the column counter BPL newtl ; Loop back until we have set all three character blocks ; on the left edge of this character row to the ; black/black palette ; And now we set the palette to black on black for the ; outside three character blocks on the right side of ; the screen, so they also show nothing LDY #37 ; Set Y = 2 to use as a column counter for the three ; character blocks, so we work our way through columns ; 37, 38 and 39 STA (ZP),Y ; Set the colour data for column 37 to the black/black ; palette INY ; Set the colour data for column 38 to the black/black STA (ZP),Y ; palette INY ; Set the colour data for column 39 to the black/black STA (ZP),Y ; palette LDA ZP ; Set ZP(1 0) = ZP(1 0) + 40 CLC ; ADC #40 ; So ZP(1 0) points to the next character row in screen STA ZP ; RAM (as there are 40 character blocks on each row) BCC P%+4 INC ZP+1 DEX ; Decrement the row counter in X BNE LOOP11 ; Loop back until we have set the colour data for the ; left and right border box edges in the space view ; Finally, we set the colour data for the bottom row in ; the text view, so the bottom of the border box is also ; shown in yellow LDA #$70 ; Set A to the colour byte that we want to apply to the ; border box, which is $70 to set the palette to ; foreground colour 7 (yellow) and background colour 0 ; (black) LDY #31 ; Set a counter in Y to work through the 31 character ; columns in the text view .LOOP16 STA $63C4,Y ; Set the colour data for column Y + 4 on row 24 to ; yellow on black ; ; The address breaks down as follows: ; ; $63C4 = $6000 + 24 * 40 + 4 ; ; So $63C4 + Y is column Y + 4 on row 24 and this loop ; sets the colour for the bottom character row of the ; text view DEY ; Decrement the column counter BPL LOOP16 ; Loop back until we have set the colour for the bottom ; border box in the text viewName: Elite loader (Part 5 of 7) [Show more] Type: Subroutine Category: Loader Summary: Configure the screen bitmap and copy colour data into screen RAM Deep dive: Colouring the Commodore 64 bitmap screenContext: See this subroutine on its own page References: No direct references to this subroutine in this source file; First we reset the contents of colour RAM, which we ; use to determine the colour of the dashboard (along ; with the space view's screen RAM, which we already ; set up in part 5) LDA #0 ; Set A = 0, so we can use this to zero the contents of ; colour RAM STA ZP ; Zero the low byte of ZP(1 0) TAY ; Set Y = 0 to use as a byte counter in the following ; loop LDX #HI(COLMEM) ; Set ZP(1 0) = COLMEM STX ZP+1 ; ; So ZP(1 0) points to colour RAM at COLMEM ($D800) LDX #4 ; Set X = 4 so we zero all four pages of colour RAM .LOOP19 STA (ZP),Y ; Zero the Y-th byte of colour RAM at SC(1 0) INY ; Increment the byte counter BNE LOOP19 ; Loop back until we have zeroed a whole page of ; colour RAM INC ZP+1 ; Increment the high byte of ZP(1 0) to point to the ; next page to zero DEX ; Decrement the page counter in X BNE LOOP19 ; Loop back until we have zeroed all four pages from ; COLMEM to COLMEM + $3FF ($D800 to $DBFF) LDA #LO(COLMEM+$2D0) ; Set ZP(1 0) to the address within the space view's STA ZP ; colour RAM that corresponds to the dashboard (i.e. LDA #HI(COLMEM+$2D0) ; offset $2D0 within the colour RAM at COLMEM, or $DAD0) STA ZP+1 LDA #LO(cdump) ; Set (A ZP2) = cdump STA ZP2 LDA #HI(cdump) JSR mvsm ; Call mvsm to copy 280 bytes of data from cdump to the ; dashboard's colour RAM for the space view, so this ; sets the correct colour data for the dashboard (along ; with the data that we already copied into screen RAM ; in part 5) ; Finally, we set the top row of colour RAM to yellow, ; so the top of the border box in the space view is ; shown in the correct colour in the event of the raster ; interrupt firing slightly late ; ; To ensure we don't get a flicker effect on the top row ; of the screen, we set colour RAM for the top row to ; $07, which sets colour %11 in the multicolour bitmap ; mode to colour 7 (yellow) ; ; The top border is drawn with bytes of %11111111, which ; maps to pixels of colour %11, so this ensures that if ; the switch to standard bitmap mode at the top of the ; screen is delayed (by non-maskable interrupts, for ; example), the VIC will fetch the colour of the top ; border box from colour RAM, so the colour will still ; be correct LDY #34 ; Set Y to a character counter so we set colour RAM for ; characters 3 to 36 on the top row LDA #$07 ; Set the low nibble of A to colour 7 (yellow), as this ; is where multicolour bitmap mode gets the palette for ; colour %11 .LOOP15 STA COLMEM+2,Y ; Set the palette to yellow for character Y DEY ; Decrement the counter in Y BNE LOOP15 ; Loop back until we have set the correct colour for the ; whole top row of the space viewName: Elite loader (Part 6 of 7) [Show more] Type: Subroutine Category: Loader Summary: Copy colour data into colour RAM and configure more screen RAM Deep dive: Colouring the Commodore 64 bitmap screenContext: See this subroutine on its own page References: No direct references to this subroutine in this source file; We now set the sprite pointers to point to the sprite ; definitions (the sprites themselves are defined in ; elite-sprite.asm) LDA #SPOFF% ; The first sprite definition at offset SPOFF% contains ; the sights for the pulse laser, so we start by setting ; Y to the sprite pointer for the first sprite, which is ; for the pulse laser (the sprites are defined in ; elite-sprite.asm) STA $63F8 ; Set the pointer for sprite 0 in the text view to A ; ; The sprite pointer for sprite 0 is at $63F8 for the ; text view because screen RAM for the text view is ; at $6000 to $63FF, and the sprite pointers always ; live in the last eight bytes of screen RAM, so that's ; from $63F8 to $63FF for sprites 0 to 7 STA $67F8 ; Set the pointer for sprite 0 in the space view to A ; ; The sprite pointer for sprite 0 is at $67F8 for the ; space view because screen RAM for the space view is ; at $6400 to $67FF, and the sprite pointers always ; live in the last eight bytes of screen RAM, so that's ; from $67F8 to $67FF for sprites 0 to 7 ; Next we set the sprite pointer for the explosion ; sprite in sprite 1 LDA #SPOFF%+4 ; There are four laser sight sprite definitions, so to ; get the offset of the fifth sprite definition, for ; the explosion sprite, we need to set A to the sprite ; offset plus 4 (as each increment in the pointer adds ; 64 bytes to the address, or one sprite definition) STA $63F9 ; Set the pointer for sprite 1 in the text view to A STA $67F9 ; Set the pointer for sprite 1 in the space view to A ; Next we set the sprite pointers for the Trumbles in ; sprites 2, 4 and 6, so they all look to the right LDA #SPOFF%+5 ; Set A to the sprite pointer for the sixth sprite ; definition (i.e. the first Trumble sprite, which ; looks to the right) STA $63FA ; Set the pointer for sprite 2 in the text view to A STA $67FA ; Set the pointer for sprite 2 in the space view to A STA $63FC ; Set the pointer for sprite 4 in the text view to A STA $67FC ; Set the pointer for sprite 4 in the space view to A STA $63FE ; Set the pointer for sprite 6 in the text view to A STA $67FE ; Set the pointer for sprite 6 in the space view to A ; And finally we set the sprite pointers for Trumble ; sprites 3, 5 and 7, so they all look to the left LDA #SPOFF%+6 ; Set A to the sprite pointer for the seventh sprite ; definition (i.e. the second Trumble sprite, which ; looks to the left) STA $63FB ; Set the pointer for sprite 3 in the text view to A STA $67FB ; Set the pointer for sprite 3 in the space view to A STA $63FD ; Set the pointer for sprite 5 in the text view to A STA $67FD ; Set the pointer for sprite 5 in the space view to A STA $63FF ; Set the pointer for sprite 7 in the text view to A STA $67FF ; Set the pointer for sprite 7 in the space view to A LDA L1 ; Set bits 0 to 2 of the 6510 port register at location AND #%11111000 ; L1 to %110 to set the input/output port to the ORA #%00000110 ; following: STA L1 ; ; * LORAM = 0 ; * HIRAM = 1 ; * CHAREN = 1 ; ; This sets the entire 64K memory map to RAM except for ; the I/O memory map at $D000-$DFFF, which gets mapped ; to registers in the VIC-II video controller chip, the ; SID sound chip, the two CIA I/O chips, and so on, and ; $E000-$FFFF, which gets mapped to the Kernal ROM ; ; See the memory map at the bottom of page 264 in the ; Programmer's Reference Guide CLI ; Allow interrupts again LDX #9 ; Set X = $16 so we copy 9 pages of data from DIALS ; into DSTORE% LDA #LO(DSTORE%) ; Set ZP(1 0) = DSTORE% STA ZP LDA #HI(DSTORE%) STA ZP+1 LDA #LO(DIALS) ; Set (A ZP2) = DIALS STA ZP2 LDA #HI(DIALS) JSR mvblock ; Call mvblock to copy 9 pages of data from DIALS to ; DSTORE%, so this makes a copy of the dashboard bitmap ; that can be poked into screen memory when the ; dashboard needs to be redrawn (when changing from a ; text view to the space view, for example) LDY #0 ; Finally, we copy two pages of sprite definitions from ; spritp to SPRITELOC%, which is where the game expects ; to find them .LOOP12 LDA spritp,Y ; Copy the Y-th byte of the sprite definitions at spritp STA SPRITELOC%,Y ; to the Y-th byte of SPRITELOC% DEY ; Decrement the byte counter BNE LOOP12 ; Loop back until we have copied a whole page of bytes .LOOP13 LDA spritp+$100,Y ; Copy the Y-th byte of the second page of sprite STA SPRITELOC%+$100,Y ; definitions at spritp + $100 into SPRITELOC% DEY ; Decrement the byte counter BNE LOOP13 ; Loop back until we have copied a second page of bytes JMP $CE0E ; This loader was originally run from the GMA1 disk ; loader, which set a return address in $CE0E before ; running the above ; ; This therefore returns us to the GMA1 loader, so it ; can load the game binary and finally run the gameName: Elite loader (Part 7 of 7) [Show more] Type: Subroutine Category: Loader Summary: Set up the sprite pointers, make a copy of the dashboard bitmap in DSTORE% and copy the sprite definitions to SPRITELOC% Deep dive: Sprite usage in Commodore 64 EliteContext: See this subroutine on its own page References: No direct references to this subroutine in this source file.mvblock STA ZP2+1 ; Set ZP2(1 0) = (A ZP2) LDY #0 ; Set Y = 0 to count through the bytes in each page .LOOP5 LDA (ZP2),Y ; Copy the Y-th byte of ZP2(1 0) to the Y-th byte of STA (ZP),Y ; ZP(1 0) DEY ; Decrement the byte counter to point to the next byte BNE LOOP5 ; Loop back to LOOP5 until we have copied a whole page INC ZP2+1 ; Increment the high byte of ZP2(1 0) to point to the ; next page to copy from INC ZP+1 ; Increment the high byte of ZP(1 0) to point to the ; next page to copy into DEX ; Decrement the page counter in X BNE LOOP5 ; Loop back to copy the next page until we have copied ; all of them RTS ; Return from the subroutineName: mvblock [Show more] Type: Subroutine Category: Loader Summary: Copy a number of pages in memoryContext: See this subroutine on its own page References: This subroutine is called as follows: * Elite loader (Part 2 of 7) calls mvblock * Elite loader (Part 7 of 7) calls mvblock * mvsm calls mvblock
Arguments: (A ZP2) The source address ZP(1 0) The destination address X The number of pages to copy.mvsm LDX #1 ; Set X = 1 to pass to mvblock so it copies one page of ; data JSR mvblock ; Call mvblock to copy 1 page of data (256 bytes) from ; (A ZP2) to ZP(1 0) LDY #23 ; We now want to copy the next 24 bytes to give a total ; of 280 bytes (as 256 + 24 = 280), so set a byte ; counter in Y LDX #1 ; Set X = 1 (though this has no effect, so this is ; presumably left over from development) .LOOP5new LDA (ZP2),Y ; Copy the Y-th byte of ZP2(1 0) to the Y-th byte of STA (ZP),Y ; ZP(1 0) DEY ; Decrement the byte counter to point to the next byte BPL LOOP5new ; Loop back to LOOP5new until we have copied all ; 24 bytes LDX #0 ; Set X = 0 RTS ; Return from the subroutineName: mvsm [Show more] Type: Subroutine Category: Loader Summary: Copy 280 bytes in memoryContext: See this subroutine on its own page References: This subroutine is called as follows: * Elite loader (Part 5 of 7) calls mvsm * Elite loader (Part 6 of 7) calls mvsm
Arguments: (A ZP2) The source address ZP(1 0) The destination address.sdump EQUB $00, $00, $00, $07, $17, $17, $74, $74 EQUB $74, $74, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $67, $27, $27, $27 EQUB $27, $27, $37, $37, $07, $00, $00, $00 EQUB $00, $00, $00, $07, $17, $17, $24, $24 EQUB $24, $24, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $67, $67, $67, $67, $23, $23 EQUB $23, $23, $37, $37, $07, $00, $00, $00 EQUB $00, $00, $00, $07, $37, $37, $29, $29 EQUB $29, $29, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $67, $27, $23, $23 EQUB $23, $23, $37, $37, $07, $00, $00, $00 EQUB $00, $00, $00, $07, $37, $37, $28, $28 EQUB $28, $28, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $24, $24 EQUB $24, $24, $17, $17, $07, $00, $00, $00 EQUB $00, $00, $00, $07, $37, $37, $2A, $2A EQUB $2A, $2A, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $24, $24 EQUB $24, $24, $17, $17, $07, $00, $00, $00 EQUB $00, $00, $00, $07, $37, $37, $2D, $2D EQUB $2D, $2D, $27, $07, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $07, $27, $24, $24 EQUB $24, $24, $17, $17, $07, $00, $00, $00 EQUB $00, $00, $00, $07, $C7, $C7, $07, $07 EQUB $07, $07, $27, $07, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $27, $27, $27, $27 EQUB $27, $27, $27, $27, $07, $27, $24, $24 EQUB $24, $24, $17, $17, $07, $00, $00, $00 IF _GMA_RELEASE EQUB $60, $D3 ; These bytes appear to be unused and just contain EQUB $66, $1D ; random workspace noise left over from the BBC Micro EQUB $A0, $40 ; assembly process EQUB $B3, $D3 ELIF _SOURCE_DISK_BUILD EQUB $B4, $48 ; These bytes appear to be unused and just contain EQUB $9F, $CD ; random workspace noise left over from the BBC Micro EQUB $EA, $11 ; assembly process EQUB $F1, $19 ELIF _SOURCE_DISK_FILES EQUB $99, $02 ; These bytes appear to be unused and just contain EQUB $E5, $6B ; random workspace noise left over from the BBC Micro EQUB $26, $B9 ; assembly process EQUB $37, $D7 ENDIFName: sdump [Show more] Type: Variable Category: Drawing the screen Summary: Screen RAM colour data for the dashboard Deep dive: Colouring the Commodore 64 bitmap screenContext: See this variable on its own page References: This variable is used as follows: * Elite loader (Part 5 of 7) uses sdump
The sdump and cdump variables contain screen and colour RAM that sets the default colours for the dashboard..cdump EQUB $00, $00, $00, $00, $05, $05, $05, $05 EQUB $05, $05, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $05, $05, $05, $05, $05, $05 EQUB $05, $05, $05, $05, $00, $00, $00, $00 EQUB $00, $00, $00, $00, $05, $05, $05, $05 EQUB $05, $05, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $05, $05, $05, $05, $05, $05 EQUB $05, $05, $05, $05, $00, $00, $00, $00 EQUB $00, $00, $00, $00, $05, $05, $05, $05 EQUB $05, $05, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $05, $05, $05, $05, $05, $05 EQUB $05, $05, $05, $05, $00, $00, $00, $00 EQUB $00, $00, $00, $00, $05, $05, $05, $05 EQUB $05, $05, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $05, $05, $05, $05, $05 EQUB $05, $05, $05, $05, $00, $00, $00, $00 EQUB $00, $00, $00, $00, $05, $05, $05, $05 EQUB $05, $05, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $05, $05 EQUB $05, $05, $05, $05, $00, $00, $00, $00 EQUB $00, $00, $00, $00, $05, $05, $05, $05 EQUB $05, $05, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $05, $05 EQUB $05, $05, $05, $05, $00, $00, $00, $00 EQUB $00, $00, $00, $00, $0F, $0F, $07, $07 EQUB $07, $07, $0D, $0D, $0D, $0D, $0D, $0D EQUB $0D, $03, $03, $03, $03, $03, $0D, $0D EQUB $0D, $0D, $0D, $0D, $0D, $0D, $07, $07 EQUB $07, $07, $05, $05, $00, $00, $00, $00 IF _GMA_RELEASE EQUB $8D, $18 ; These bytes appear to be unused and just contain EQUB $8F, $50 ; random workspace noise left over from the BBC Micro EQUB $46, $7E ; assembly process EQUB $A4, $F4 ELIF _SOURCE_DISK_BUILD EQUB $B3, $56 ; These bytes appear to be unused and just contain EQUB $2B, $6B ; random workspace noise left over from the BBC Micro EQUB $74, $D4 ; assembly process EQUB $D8, $FF ELIF _SOURCE_DISK_FILES EQUB $00, $FB ; These bytes appear to be unused and just contain EQUB $0E, $F3 ; random workspace noise left over from the BBC Micro EQUB $79, $7D ; assembly process EQUB $48, $96 ENDIFName: cdump [Show more] Type: Variable Category: Drawing the screen Summary: Colour RAM colour data for the dashboard Deep dive: Colouring the Commodore 64 bitmap screenContext: See this variable on its own page References: This variable is used as follows: * Elite loader (Part 6 of 7) uses cdump
The sdump and cdump variables contain screen and colour RAM that sets the default colours for the dashboard..spritp INCBIN "3-assembled-output/SPRITE.bin" IF _GMA_RELEASE EQUB $38, $35, $25, $67, $FA, $B5, $A5, $A2 ; These bytes appear to be EQUB $22, $C1, $DF, $EB, $77, $CE, $F4, $07 ; unused and just contain random EQUB $37, $CF, $33, $4D, $A5, $89, $76, $CD ; workspace noise left over from EQUB $6D, $69, $8D, $56, $CD, $94, $98, $F6 ; the BBC Micro assembly process EQUB $B8, $CE, $14, $13, $D1, $98, $CE, $B1 EQUB $77, $CE, $F4, $1C, $B1, $40, $68, $30 EQUB $87, $CD, $A9, $90, $B2, $08, $C1, $DB EQUB $CF, $33, $49, $80, $6B, $CA, $3A, $CF ELIF _SOURCE_DISK_BUILD EQUB $97, $F3, $4F, $73, $B6, $DB, $39, $7A ; These bytes appear to be EQUB $56, $EE, $F5, $D3, $4F, $E4, $C4, $F5 ; unused and just contain random EQUB $FE, $05, $D3, $4F, $68, $91, $3E, $F9 ; workspace noise left over from EQUB $00, $D3, $4F, $27, $53, $41, $F6, $FD ; the BBC Micro assembly process EQUB $D6, $26, $CB, $24, $C5, $ED, $14, $3C EQUB $E9, $F0, $D3, $4F, $62, $8E, $41, $F1 EQUB $F8, $D3, $4F, $30, $5F, $44, $05, $0C EQUB $D3, $4F, $68, $99, $A1, $CB, $B7, $34 ELIF _SOURCE_DISK_FILES EQUB $DC, $80, $1F, $87, $29, $80, $80, $E3 ; These bytes appear to be EQUB $8A, $42, $CE, $41, $9D, $20, $CB, $DC ; unused and just contain random EQUB $44, $E3, $C8, $22, $33, $A8, $B9, $F3 ; workspace noise left over from EQUB $03, $D8, $22, $B7, $F9, $CF, $37, $F9 ; the BBC Micro assembly process EQUB $D3, $22, $76, $7A, $94, $37, $F3, $D3 EQUB $FC, $F1, $EF, $E9, $B2, $01, $50, $25 EQUB $D9, $C3, $22, $B1, $F0, $CF, $32, $E9 EQUB $CB, $22, $7F, $8F, $A3, $49, $11, $48 ENDIFName: spritp [Show more] Type: Variable Category: Drawing the screen Summary: Sprite definitionsContext: See this variable on its own page References: This variable is used as follows: * Elite loader (Part 7 of 7) uses spritp.date IF _SOURCE_DISK INCBIN "1-source-files/images/C.DATE4.bin" ELIF _GMA_RELEASE EQUB $33, $8D, $49, $EA, $53, $29, $2C, $2F ; These bytes appear to be EQUB $87, $C4, $A0, $70, $96, $90, $B3, $38 ; unused and just contain random EQUB $B9, $53, $9A, $91, $AE, $2E, $70, $F8 ; workspace noise left over from EQUB $C8, $1B, $7C, $A1, $D1, $37, $2B, $4C ; the BBC Micro assembly process EQUB $97, $F3, $4F, $73, $AD, $D2, $39, $71 ; EQUB $4D, $EE, $F5, $D3, $4F, $E7, $C7, $F5 ; They contain part of the EQUB $FE, $05, $D3, $4F, $68, $88, $35, $F9 ; encrypted HICODE binary, from EQUB $00, $D3, $4F, $27, $4A, $38, $F6, $FD ; file offset $1C8A to $1D89, EQUB $D6, $26, $CB, $1B, $BC, $ED, $0B, $33 ; from when it was assembled in EQUB $E9, $F0, $D3, $4F, $62, $85, $38, $F1 ; memory EQUB $F8, $D3, $4F, $30, $56, $3B, $05, $0C EQUB $D3, $4F, $68, $90, $98, $CB, $B7, $34 EQUB $ED, $01, $08, $D3, $4F, $07, $2F, $3D EQUB $D1, $D8, $D3, $4F, $62, $83, $36, $DB EQUB $E2, $DB, $2B, $07, $71, $1A, $93, $4F EQUB $F8, $34, $D4, $33, $6F, $51, $CE, $D5 EQUB $EA, $66, $8D, $AF, $37, $04, $2B, $FE EQUB $D7, $03, $2A, $F7, $D0, $06, $0D, $DB EQUB $AD, $A5, $2F, $CE, $A4, $2E, $CE, $A3 EQUB $4D, $06, $60, $D2, $5B, $BC, $9D, $13 EQUB $4F, $A8, $CD, $3A, $F7, $1E, $3E, $17 EQUB $F4, $FB, $DD, $B2, $4C, $97, $35, $EA EQUB $45, $C9, $E9, $B0, $2F, $8B, $12, $F7 EQUB $B6, $8B, $AB, $45, $C9, $E9, $B0, $06 EQUB $BB, $0B, $36, $E2, $B7, $AB, $CF, $E3 EQUB $EA, $D9, $29, $A2, $F1, $8F, $B5, $D3 EQUB $8A, $CE, $F1, $8F, $75, $C4, $14, $0B EQUB $56, $0A, $E0, $2B, $35, $E6, $BC, $0C EQUB $30, $EA, $44, $96, $1B, $AE, $8A, $EA EQUB $0B, $0C, $86, $44, $96, $38, $2C, $36 EQUB $D3, $4F, $29, $50, $D3, $05, $45, $C9 EQUB $E9, $B0, $E9, $19, $B5, $0B, $FB, $B9 ENDIFName: date [Show more] Type: Variable Category: Loader Summary: A date image that is included into the source disk binaries (this is just random noise in the released game)Context: See this variable on its own page References: No direct references to this variable in this source file.DIALS SKIP 24 ; This indents the image by three character blocks to ; skip past the first three characters of the left ; screen margin (the fourth character contains the ; border box along the edge of the dashboard) INCBIN "1-source-files/images/C.CODIALS.bin" IF _GMA_RELEASE EQUB $F5 ; This byte appears to be unused and just contains ; random workspace noise left over from the BBC Micro ; assembly process ELIF _SOURCE_DISK_BUILD EQUB $B2 ; This byte appears to be unused and just contains ; random workspace noise left over from the BBC Micro ; assembly process ELIF _SOURCE_DISK_FILES EQUB $DB ; This byte appears to be unused and just contains ; random workspace noise left over from the BBC Micro ; assembly process ENDIFName: DIALS [Show more] Type: Variable Category: Drawing the screen Summary: The dashboard bitmap and colour data for screen RAMContext: See this variable on its own page References: This variable is used as follows: * Elite loader (Part 7 of 7) uses DIALS.V% SKIP 0Name: V% [Show more] Type: Variable Category: Utility routines Summary: Denotes the end of the second block of loader code, as used in the encryption/decryption processContext: See this variable on its own page References: This variable is used as follows: * Elite loader (Part 1 of 7) uses V%PRINT "P% = ", ~P% PRINT "S.C.COMLOD ", ~CODE%, " ", ~P%, " ", ~LOAD%, " ", ~LOAD% SAVE "3-assembled-output/COMLOD.unprot.bin", CODE%, P%, LOAD% PRINT "Addresses for the scramble routines in elite-checksum.py" PRINT "W% = ", ~W% PRINT "X% = ", ~X% PRINT "U% = ", ~U% PRINT "V% = ", ~V%Save COMLOD.unprot.bin
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Configuration variable CIA
Registers for the CIA1 I/O interface chip, which are memory-mapped to the 16 bytes from $DC00 to $DC0F (see page 428 of the Programmer's Reference Guide)
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Configuration variable CIA2
Registers for the CIA2 I/O interface chip, which are memory-mapped to the 16 bytes from $DD00 to $DD0F (see page 428 of the Programmer's Reference Guide)
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Configuration variable COLMEM
Colour RAM, which is used (along with screen RAM) to define the colour map of the dashboard in multicolour bitmap mode
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Configuration variable D%
The address where the ship data will be loaded (i.e. XX21)
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Subroutine DEEORS (category: Loader)
Decrypt a multi-page block of memory
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Variable DIALS (category: Drawing the screen)
The dashboard bitmap and colour data for screen RAM
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Configuration variable DSTORE%
The address of a copy of the dashboard bitmap, which gets copied into screen memory when setting up a new screen
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Variable FRIN (category: Loader)
A temporary variable that's used for storing addresses
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Configuration variable KEY3
The seed for decrypting COMLOD from U% to V%, which is the second block of data, after the decryption routine
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Configuration variable KEY4
The seed for decrypting COMLOD from W% to X%, which is the first block of data, before the decryption routine
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Configuration variable L1
The 6510 input/output port register, which we can use to configure the Commodore 64 memory layout (see page 260 of the Programmer's Reference Guide)
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Subroutine LODATA (category: Loader)
The binaries for recursive tokens and the game font
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Label LOOP1 in subroutine Elite loader (Part 5 of 7)
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Label LOOP10 in subroutine Elite loader (Part 5 of 7)
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Label LOOP11 in subroutine Elite loader (Part 5 of 7)
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Label LOOP12 in subroutine Elite loader (Part 7 of 7)
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Label LOOP13 in subroutine Elite loader (Part 7 of 7)
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Label LOOP15 in subroutine Elite loader (Part 6 of 7)
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Label LOOP16 in subroutine Elite loader (Part 5 of 7)
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Label LOOP19 in subroutine Elite loader (Part 6 of 7)
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Label LOOP2 in subroutine Elite loader (Part 5 of 7)
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Label LOOP3 in subroutine Elite loader (Part 5 of 7)
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Label LOOP4 in subroutine Elite loader (Part 5 of 7)
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Configuration variable SCBASE
The address of the screen bitmap
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Subroutine SHIPS (category: Loader)
The binaries for the ship blueprints
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Configuration variable SPOFF%
Sprite pointers are defined as the offset from the start of the VIC-II screen bank to start of the sprite definitions, divided by 64, so SPOFF% is the offset for the first sprite definition at SPRITELOC%
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Configuration variable SPRITELOC%
The address where the sprite bitmaps get copied to during the loading process
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Label U% in subroutine Elite loader (Part 2 of 7)
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Variable V% (category: Utility routines)
Denotes the end of the second block of loader code, as used in the encryption/decryption process
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Configuration variable VIC
Registers for the VIC-II video controller chip, which are memory-mapped to the 46 bytes from $D000 to $D02E (see page 454 of the Programmer's Reference Guide)
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Variable W% (category: Utility routines)
Denotes the start of the first block of loader code, as used in the encryption/decryption process
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Variable X% (category: Utility routines)
Denotes the end of the first block of loader code, as used in the encryption/decryption process
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Workspace ZP (category: Workspaces)
Important variables used by the loader
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Variable cdump (category: Drawing the screen)
Colour RAM colour data for the dashboard
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Label frogl in subroutine Elite loader (Part 5 of 7)
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Subroutine mvblock (category: Loader)
Copy a number of pages in memory
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Subroutine mvsm (category: Loader)
Copy 280 bytes in memory
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Label newtl in subroutine Elite loader (Part 5 of 7)
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Variable sdump (category: Drawing the screen)
Screen RAM colour data for the dashboard
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Variable spritp (category: Drawing the screen)
Sprite definitions