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6502_linux_logo
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; 6502 Linux Logo
; Michaelangel007
; https://github.com/Michaelangel007/6502_linux_logo
; Zero Page ROM vars
zCursorX = $24 ; CH
zCursorY = $25 ; CH
; NOTE: We *don't* use this, instead we *re-use* zTxtPtr
;zHgrPtr = $26 ; GBASL = Dst Pixel Addr
zTxtPtr = $28 ; BASL = Dst
zDstOffset = $F9 ; dst
zSrcOffset = $FA ; src
zMask = $FB ; adjacent byte to write next pixels
zSrcShift = $FC ; Input Bit Position = i mod 8
zDstShift = $FD ; Output Bit Position = i mod 7
zUnpackBits = $FE ; 16-bit unpack
; ROM
HOME = $FC58
COUT = $FDED
IB_HGR = $D000 ; Integer BASIC ][ only
AS_HGR = $F3E2 ; Applesoft BASIC ][+ or newer
BASCALC = $FBC1 ; A=Row, Calculate BASL,BASH text start-of-line address
;Bank Addr -- Addr Bank Read --- Write -------
; 2 $C080 == $C088 1 Read RAM Write protect
; 2 $C081 == $C089 1 Read ROM Write enabled
; 2 $C082 == $C08A 1 Read ROM Write protect
; 2 $C083 == $C08B 1 Read RAM Write enabled
RAMIN = $C080
ROMIN = $C081
MACHINEID1 = $FBB3
MACHINEID2 = $FBC0
MACHINEID3 = $FBBF ; //c version
; Config
UnpackAddr = $3FD0 ; Y=191, Unpacked pixel buffer of $28 bytes
CONFIG_PROBE_CPUINFO = 1
CONFIG_PRINT_CPUINFO = 1
; ========================================================================
ORG $900
Main
jsr HOME ; For asethetics
; ------------------------------------------------------------------------
; Apple II Technical Note #7
; https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Computers/Apple%20II/Apple%20II/Documentation/Misc%20%23007%20Apple%20II%20Family%20ID.pdf
;
; Machine $FBB3 $FBC0 $FBBE
; Apple ][ $38
; Apple ][+ $EA
; Apple /// $EA
; Apple //e $06 $EA
; Apple //e+ $06 $E0
; Apple //e Option Card $06 $E0
; Apple //c $06 $00 $FF
; Apple //c 3.5 $06 $00 $00
; Apple //c Org Mem XP $06 $00 $03
; Apple //c Rev Mem XP $06 $00 $04
; Apple //c+ $06 $00 $05
; Apple IIgs
DO CONFIG_PROBE_CPUINFO
detect_model
lda MACHINEID1 ; FBB3: $38 = ][, $EA = ][+, $06 = //e //c IIgs
cmp #$38 ; '8'
beq apple_ii
pha
jsr AS_HGR ; HGR on Apple ][+ or newer
pla
cmp #$EA ; 'j' apple ][+?
bne apple_iie_iic ; if so keep going
apple_iiplus
; if we get here we're a ii+ or iii in emulation mode
lda #"+"
bne set_apple_ii
apple_ii
jsr IB_HGR ; HGR on original ][ only!
lda #" " ; "_6502"
set_apple_ii
ldx #"]"
ldy #"["
stx ModType-2
sty ModType-1
sta ModType ; erase last 'e' in 'Apple IIe'
lda #" " ; "_6502"
sta CpuType ; ^^^
ldx #"6"
ldy #"5"
stx CpuType+1
sty CpuType+2
detect_langcard
sta RAMIN ; Detect 16K RAM / Language Card
sta RAMIN ; Read RAM
lda $D000
inc $D000
cmp $D000
beq apple_ii_48K
dec $D000
RAM_64K
ldx #"6" ; "64K"
ldy #"4"
bne RAM_size
apple_ii_48K
ldx #"4"
ldy #"8"
RAM_size
lda #" "
sta RamSize ; erase '1' in '128'
stx RamSize+1
sty RamSize+2
bne done_detecting
; Detect //e //e+ //c //c+
apple_iie_iic
lda MACHINEID2 ; FBC0: $00 = //c, $EA = //e, E0 = //e+
beq apple_iic ; check for apple //c
cmp #$E0 ; if we're an Apple IIe (original)
bne RAM_64K ; then use 64K and finish
beq apple_iie_enhanced
apple_iic
lda #"c"
sta CpuType+1
lda MACHINEID3
cmp #$05 ; //c+
bne done_detecting
apple_iie_enhanced ; //e+
lda #"+" ; +
sta ModType+1 ; ^
done_detecting
sta ROMIN ; Turn off Language Card
; sta ROMIN ; if it was probed
FIN
; ------------------------------------------------------------------------
; Unpack 2 bits/color -> $28 bytes/scanline
;
; Unpack one line to buffer at Y=191 HGR line
; Copy to 8 scanlines
; Erase buffer after copying to final 8 scanlines
Unpack
DO 1-CONFIG_PROBE_CPUINFO
jsr AS_HGR ; *** DEBUG ***
FIN
lda #7 ; will INC, $0428 (Text) + $1C00 => $2028 (HGR)
sta zCursorY ; Start Row=8
ldy #0 ; zSrcOffset
sty zDstShift
sty zDstOffset
lda PackedBits
sta zUnpackBits+0
NextSrcShift
lda PackedBits+1,Y
sta zUnpackBits+1
ldx #8 ; zSrcShift, have 8 input bits?
UpdateSrcShift
stx zSrcShift
jsr Unpack2Bits ; hhggffee C=? ddccbbaa
bcs UnpackDone ; inlining Unpack2Bits has BNE and BNE > 128 byte offset
lsr zUnpackBits+1 ; 0hhggffe C=e ddccbbaa
ror zUnpackBits+0 ; 0hhggffe C=e eddccbba
lsr zUnpackBits+1 ; 00hhggff C=e eddccbba
ror zUnpackBits+0 ; 00hhggff c=e eeddccbb
ldx zSrcShift
dex
dex
bne UpdateSrcShift
iny ; src++
bne NextSrcShift ; always, since packed data length < 256
UnpackDone
; ------------------------------------------------------------------------
DO CONFIG_PRINT_CPUINFO
txa ; (2) X=$14 from (1) Unpack2Bits
jsr BASCALC ; but we can't see it since we are in mixed mode
ldx #0 ; This means we have an extra "row" of HGR garbage at Y=160
CopyTextLine
lda TextLine,X
jsr COUT
inx
cpx #106 ; 3 rows of 40-col text but stop at col 27
bne CopyTextLine
rts
FIN
; ========================================================================
; NOTE: Normally there is
; rts
; but to save a byte we intentionally fall into Unpack2Bits in 2 locations:
;
; A) if we reach
; apple_iie_enhanced
; B) end of program
;
; This means there is an extremely rare bug of having extra garbage
; on the HGR screen for (A) under these conditions:
;
; F9:27 <- zDstOffset = column 39
; FE:0x <- non-zero value bottom 2 bits are set
;
; To trigger:
; CALL-151
; BLOAD LINUXLOGO
; F9:27
; FE:02
; 900G
; Or on two lines
; BLOAD LINUXLOGO
; F9:27 N FE:2 N 900G
; And a thin blue line will appear in the top right
; ========================================================================
; ------------------------------------------------------------------------
; Expand 1 pixel (2 bits) via
; Output 2 pixels (4 bits)
Unpack2Bits
sty zSrcOffset
lda zUnpackBits ; Double the pixel
asl ; A=?????ba0
asl ; A=????ba00
eor zUnpackBits ; A=????xxyy
and #%00001100 ; A=????xx00
eor zUnpackBits ; A=????baba
and #%00001111 ; A=0000baba
ldx #0
stx zMask
ldy zDstShift ; which 280 px column is next pixel writing to?
MakeShiftMask
asl ; msb of byte0 set?
rol zMask ; shift in to lsb of byte1
dey
bpl MakeShiftMask
sec ; MSB=1 color=blue/orange
ror
ldx zDstOffset
ora UnpackAddr,X ; do all bits that fit
sta UnpackAddr,X
lda zDstShift ; x={0,1,2} + 4 < 7
adc #4 ; C=0 from ASL ROR above
cmp #7 ; all bits fit into dest byte?
bcc FitSameByte
; Update partial next byte of dest
; x = x + 4 - 7
sbc #7 ; C=1 from "BCC else" above
tay ; push zDstShift
inx
stx zDstOffset
lda zMask
ora UnpackAddr,X
sta UnpackAddr,X
tya ; pop zDstShift
cpx #$28 ; C = x < 28
bcc FitSameByte ; C = x < 28
; ------------------------------------------------------------------------
; Udpate the Text Address
; Update the HGR scanline Address
inc zCursorY
lda zCursorY
jsr BASCALC
; ------------------------------------------------------------------------
; Copy unpacked buffer to 8 HGR scanlines
Draw8Rows
ldy #39 ; 280/7 = 40 bytes/scanline
; Yes, this is evil ...
; Instead of copying zTxtPtr over to zHgrPtr
; We re-use it by forcing it to be a HGR address!
; This *is* safe BECAUSE we call JSR BASCALC _before_ we do any text printing.
lda zTxtPtr+1 ; Translate text page row address to
eor #$24 ; every eighth HGR row address
tax
Copy7x8
lda UnpackAddr,Y
stx zTxtPtr+1
sta (zTxtPtr),Y
inx ; y = y+1
inx ; HGR addr_y+1 = addr_y + $0400
inx
inx
cpx #$40 ; hit HGR page 2 ? i.e. 8 scan lines done?
bcc Copy7x8 ; Loop until 7x8 pixel block is complete
txa
sbc #$20 ; Reset pointer for top of next 7x8 block
tax
lda #0
sta UnpackAddr,Y ; Clear source on last scanline copy
sta zDstOffset ; reset to start of unpack buffer
dey
bpl Copy7x8 ; Loop until all 280x8 pixels are copied
ldx zCursorY ; (1) X=14, see (2)
cpx #$14 ; Y=$40 .. $A0, Rows $8..$13 (inclusive)
FitSameByte
sta zDstShift
ldy zSrcOffset ; NOTE: C=0 from CMPs above
rts
; ========================================================================
CpuType = * + 13 + 40
RamSize = * + 30 + 40
ModType = * + 24 + 40*2
; Uppercase in case of Apple ][ without lowercase support
; 1 2 3
TextLine ;0123456789012345678901234567890123456789
ASC " LINUX VERSION 2.6.22.6, COMPILED 2007 " ; Row $14 +40 = 40
ASC " ONE 1.02MHZ 65C02 PROCESSOR, 128KB RAM " ; Row $15 +40 = 80
ASC " APPLE //e " ; Row $16 +26 = 106 chars
; ^ ^ ^
; CPUTYPE MOD RAM
; ------------------------------------------------------------------------
;"__________________________________________________________@@@@@_______"
;"_________________________________________________________@@@@@@@______"
;"______________A__________________________________________@@_@_@@______"
;"@@@@@@_______AA@_________________________________________@BBBBB@______"
;"__@@__________@________________________________________@@__BBB__@@____"
;"__@@_______AAA__@@@_@@@@___@@@____@@@__@@@@@_@@@@@____@__________@@___"
;"__@@______A__A@__@@@____@@__@@_____@@____@@___@@_____@____________@@__"
;"__@@_____A___A@__@@_____@@__@@_____@@_____@@_@@______@____________@@@_"
;"__@@________AA@__@@_____@@__@@_____@@______@@@______BB@___________@@B_"
;"__@@_____@_AA@___@@_____@@__@@_____@@_____@@_@@____BBBBB@_______@BBBBB"
;"__@@____@@_AA@_@_@@_____@@__@@@___@@@____@@___@@___BBBBBB@_____@BBBBBB"
;"@@@@@@@@@@__@@@_@@@@___@@@@___@@@@_@@@_@@@@@_@@@@@__BBBBB@@@@@@@BBBBB_"
; Char &3 Color
; @ 00 Black
; A 01 Blue
; B 10 Orange
; _ 11 White
; NOTE: Generated by ascii2hgr2bit
; ASCII: 70*12 = 840 chars
; Packed 2bits/2pixel: 70 chars * 2 bits/char / 8 bits/byte = 140 bits / 8 = 17.5 bytes/scanline
; 840 chars * 2 bits/color / 8 bits/byte = 210 bytes
PUT packedlogo.s
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