mirror of
https://github.com/AppleCommander/AppleCommander.git
synced 2024-06-12 17:32:20 +00:00
44da9f8133
(2) needed to clear the keyboard (otherwise the keypress was still valid when the next disk was booted). Also needed to reduce program by a few more bytes. By changing the rotate routine and changing the wording in the message, this code is now only 254 bytes. Also added more comments.
1 line
2.9 KiB
ArmAsm
1 line
2.9 KiB
ArmAsm
**********************************************************
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* *
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* APPLECOMMANDER boot code. *
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* Copyright (c) 2002, Rob Greene *
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* *
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* This code is published under the GPL license. See the *
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* AppleCommander site for license information. *
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* *
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**********************************************************
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ORG $800
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*
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* Zero page variables. Used by Apple ][ ROM routines
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* as well as this code.
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*
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XEND = $2C
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ADDR = $26
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*
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* Keyboard switches
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*
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KEYBOARD = $C000
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KEYCLEAR = $C010
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*
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* Disk ][ interface locations
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*
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MOTOROFF = $C088
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*
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* General Apple ][ ROM locations
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*
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TEXT = $FB2F
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HOME = $FC58
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GR = $FB40
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COLOR = $F864
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HLIN = $F819
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PRINT = $FDED
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REBOOT = $FAA6
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CALCADDR = $F847
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DELAY = $FCA8
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*
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* Image offset locations (from upper-left).
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* Note that, due to space, the XOFFSET isn't
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* currently used - but, because of the rotating
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* image, it doesn't really matter!
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*
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XOFFSET = 14
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YOFFSET = 13
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*
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* The boot rom (probably $C600) uses the first byte
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* to indicate the number of sectors to load. Normally
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* this is just one sector, so this program is constrained
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* to 256 bytes - just in case of compatibility problems.
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*
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DFB 1
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*
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* General setup.
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*
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LDA MOTOROFF,X
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JSR TEXT
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JSR HOME
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JSR GR
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*
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* Draw the AppleCommander logo (well, sorta).
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* DATA1 and DATA2 contain 4 values - the color value,
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* the xstart (start of line), xend (end of line), as
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* well as the Y position.
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*
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LDX #DATA2-DATA1
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:LOGO LDA DATA1-1,X
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LSR
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LSR
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LSR
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LSR
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JSR COLOR
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LDA DATA2-1,X
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LSR
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LSR
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LSR
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LSR
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STA XEND
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LDA DATA1-1,X
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AND #$F
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TAY
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LDA DATA2-1,X
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AND #$F
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CLC
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ADC #YOFFSET
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JSR HLIN
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DEX
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BNE :LOGO
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*
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* Display AppleCommander message.
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*
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:TEXT LDA MESSAGE,X
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BEQ :WAIT
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JSR PRINT
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INX
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BNE :TEXT
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*
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* Check for a keypress
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*
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:WAIT LDA KEYBOARD
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BPL :SETUP
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STA KEYCLEAR
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JMP REBOOT
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*
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* Rotate the screen (isn't that retro)!
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*
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:SETUP LDX #19
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:ROTATE TXA
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JSR CALCADDR
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LDY #0
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LDA (ADDR),Y
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PHA
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:SHIFT INY
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LDA (ADDR),Y
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DEY
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STA (ADDR),Y
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INY
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CPY #39
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BNE :SHIFT
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PLA
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STA (ADDR),Y
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DEX
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BPL :ROTATE
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*
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* Introduce a pause between rotations.
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*
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:KEYLOOP LDA #$08
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JSR DELAY
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DEX
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BNE :KEYLOOP
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BEQ :WAIT
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*
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* The image data codes the upper nybble with one
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* value and the lower nybble with the second value
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* in an effort to conserve space. Thus, 17 HLINs
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* are stored in 34 bytes instead of 68.
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*
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* DATA1 consists of color and x1 (start) position.
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*
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DATA1 HEX C8C7C6C3C8C2 ; green
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HEX D1D1 ; yellow
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HEX 9090 ; orange
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HEX 1010 ; red
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HEX 3131 ; purple
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HEX 626368 ; blue
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*
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* DATA2 consists of x2 (end) and y position.
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*
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DATA2 HEX 90817253B3C4
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HEX D5D6
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HEX C7B8
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HEX B9CA
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HEX DBDC
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HEX CD5EBE
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*
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* Text message to display at bottom of screen.
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*
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MESSAGE ASC "THIS DISK CREATED WITH APPLECOMMANDER"8D
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ASC "VISIT APPLECOMMANDER.SF.NET"8D
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ASC " "8D
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ASC "INSERT ANOTHER DISK AND PRESS ANY KEY"00
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