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|
; COL80.COM, aka COL80E.COM, aka COL80HND.COM
; (and probably several other names)
; Original author unknown
; License unknown
; Disassembly and comments by Urchlay
; This is a widely-distributed software 80-column driver for the Atari
; 8-bit computers. It replaces the OS's E: driver, and uses GRAPHICS 8
; for display, with 4x8 pixel character cells.
; Disassembly was done with da65, with many iterations of "edit the
; .info file, disassemble again", and the results were tweaked by hand
; into something assemblable by dasm (and fairly compatible with other
; assemblers).
; START_ADDRESS is defined in col80_startaddr.s
.org START_ADDRESS
; ----------------------------------------------------------------------------
; Zero page labels (OS equates)
DOSINI = $000C
ICAX1Z = $002A
ICAX2Z = $002B
TMPCHR = $0050
LMARGN = $0052
ROWCRS = $0054
COLCRS = $0055
DINDEX = $0057
SAVMSC = $0058
BUFCNT = $006B
; ----------------------------------------------------------------------------
; Zero page labels (COL80 equates)
screen_ptr_lo = $00CB
screen_ptr_hi = $00CC
font_ptr_lo = $00CD
font_ptr_hi = $00CE
; ----------------------------------------------------------------------------
; Non-zeropage RAM labels (OS equates)
COLOR1 = $02C5
COLOR2 = $02C6
RUNAD = $02E0
MEMTOP = $02E5
SSFLAG = $02FF
HATABS = $031A
ICCOM = $0342
ICBAL = $0344
ICBAH = $0345
; ----------------------------------------------------------------------------
; Hardware (memory-mapped I/O, OS equates)
CONSOL = $D01F
AUDF1 = $D200
AUDC1 = $D201
; ----------------------------------------------------------------------------
; OS ROM labels
s_dev_open_lo = $E410 ; (not named in OS sources)
s_dev_open_hi = $E411 ; ""
k_dev_get_lo = $E424 ; ""
k_dev_get_hi = $E425 ; ""
CIOV = $E456 ; Central Input/Output entry point
; ----------------------------------------------------------------------------
; Start of COL80. The font is stored in packed form. Each group of 8 bytes
; defines two glyphs: the upper 4 bits of the 8 bytes, taken together,
; define the bitmap for the first glyph, and the lower 4 bits are the second.
; Note that the bits that make up a single character are spread across 8
; bytes, so it's hard to visualize these even if you're used to reading hex
; dumps.
; The first 2 characters look like:
; .... .O.. ; $04
; .... .O.. ; $04
; O.O. .O.. ; $A4
; OOO. .O.. ; $E4
; OOO. .OOO ; $E7
; .O.. .O.. ; $44
; .... .O.. ; $04
; .... .O.. ; $04
; These are the ATASCII heart symbol (character code 0) and the ATASCII
; control-A line-drawing symbol (code 1).
; Note: unlike the ROM font, this font is stored in ATASCII order instead
; of the standard Atari character order imposed by the hardware. Like
; the ROM font, inverse characters are not stored here (the bitmaps get
; inverted by the driver)
font_data:
; Low ATASCII graphics symbols (code 0-31)
.byte $04,$04,$A4,$E4,$E7,$44,$04,$04 ; 7A00
.byte $14,$14,$14,$14,$1C,$10,$10,$10 ; 7A08
.byte $40,$40,$40,$40,$CC,$44,$44,$44 ; 7A10
.byte $18,$18,$24,$24,$42,$42,$81,$81 ; 7A18
.byte $10,$10,$30,$30,$73,$73,$F3,$F3 ; 7A20
.byte $83,$83,$C3,$C3,$E0,$E0,$F0,$F0 ; 7A28
.byte $CF,$CF,$C0,$C0,$00,$00,$00,$00 ; 7A30
.byte $00,$00,$00,$00,$0C,$0C,$FC,$FC ; 7A38
.byte $00,$00,$00,$40,$A7,$44,$E4,$04 ; 7A40
.byte $04,$04,$04,$04,$FF,$04,$04,$04 ; 7A48
.byte $00,$00,$60,$F0,$FF,$6F,$0F,$0F ; 7A50
.byte $80,$80,$80,$80,$8F,$84,$84,$84 ; 7A58
.byte $4C,$4C,$4C,$4C,$FC,$0C,$0C,$0C ; 7A60
.byte $40,$4C,$48,$4C,$78,$0C,$06,$00 ; 7A68
.byte $00,$44,$E4,$44,$4E,$44,$00,$00 ; 7A70
.byte $00,$24,$42,$FF,$42,$24,$00,$00 ; 7A78
; Space ! " # etc (codes 32-63)
.byte $00,$04,$04,$04,$04,$00,$04,$00 ; 7A80
.byte $00,$A0,$AA,$AE,$0A,$0E,$0A,$00 ; 7A88
.byte $00,$40,$68,$82,$44,$28,$C2,$40 ; 7A90
.byte $00,$C4,$64,$E4,$60,$C0,$40,$00 ; 7A98
.byte $00,$44,$82,$82,$82,$82,$82,$44 ; 7AA0
.byte $00,$04,$A4,$4E,$E4,$44,$A0,$00 ; 7AA8
.byte $00,$00,$00,$0E,$00,$40,$40,$80 ; 7AB0
.byte $00,$02,$02,$04,$04,$08,$48,$00 ; 7AB8
.byte $00,$E4,$AC,$A4,$A4,$A4,$EE,$00 ; 7AC0
.byte $00,$EE,$22,$22,$EE,$82,$EE,$00 ; 7AC8
.byte $00,$AE,$A8,$AE,$E2,$22,$2E,$00 ; 7AD0
.byte $00,$EE,$82,$E2,$A4,$A4,$E4,$00 ; 7AD8
.byte $00,$EE,$AA,$EA,$AE,$A2,$EE,$00 ; 7AE0
.byte $00,$00,$00,$44,$00,$44,$04,$08 ; 7AE8
.byte $00,$20,$4E,$80,$4E,$20,$00,$00 ; 7AF0
.byte $00,$8C,$42,$22,$44,$80,$04,$00 ; 7AF8
; @ A B C etc (codes 64-95)
.byte $00,$6E,$9A,$BA,$BE,$8A,$6A,$00 ; 7B00
.byte $00,$C6,$A8,$C8,$A8,$A8,$C6,$00 ; 7B08
.byte $00,$CE,$A8,$AC,$A8,$A8,$CE,$00 ; 7B10
.byte $00,$E6,$88,$C8,$8A,$8A,$86,$00 ; 7B18
.byte $00,$AE,$A4,$E4,$A4,$A4,$AE,$00 ; 7B20
.byte $00,$2A,$2A,$2C,$2A,$2A,$CA,$00 ; 7B28
.byte $00,$8A,$8E,$8E,$8A,$8A,$EA,$00 ; 7B30
.byte $00,$C4,$AA,$AA,$AA,$AA,$A4,$00 ; 7B38
.byte $00,$EE,$AA,$EA,$8A,$8A,$8E,$03 ; 7B40
.byte $00,$C6,$A8,$AC,$C2,$A2,$AC,$00 ; 7B48
.byte $00,$EA,$4A,$4A,$4A,$4A,$4E,$00 ; 7B50
.byte $00,$AA,$AA,$AA,$AE,$AE,$4A,$00 ; 7B58
.byte $00,$AA,$4A,$4E,$44,$44,$A4,$00 ; 7B60
.byte $00,$EE,$28,$48,$88,$88,$E8,$0E ; 7B68
.byte $00,$8E,$82,$42,$42,$22,$22,$0E ; 7B70
.byte $00,$00,$40,$A0,$00,$00,$00,$0F ; 7B78
; diamond, lowercase letters, control codes (codes 96-127)
.byte $00,$00,$00,$46,$E2,$4E,$0E,$00 ; 7B80
.byte $00,$80,$80,$C6,$A8,$A8,$C6,$00 ; 7B88
.byte $00,$20,$20,$6E,$AE,$A8,$6E,$00 ; 7B90
.byte $00,$00,$C0,$86,$CA,$8E,$82,$0C ; 7B98
.byte $00,$80,$84,$80,$C4,$A4,$A4,$00 ; 7BA0
.byte $00,$08,$28,$0A,$2C,$2A,$2A,$C0 ; 7BA8
.byte $00,$40,$40,$4A,$4E,$4A,$4A,$00 ; 7BB0
.byte $00,$00,$00,$CE,$AA,$AA,$AE,$00 ; 7BB8
.byte $00,$00,$00,$C6,$AA,$C6,$82,$82 ; 7BC0
.byte $00,$00,$00,$6E,$88,$86,$8E,$00 ; 7BC8
.byte $00,$00,$40,$EA,$4A,$4A,$6E,$00 ; 7BD0
.byte $00,$00,$00,$AA,$AA,$AE,$4A,$00 ; 7BD8
.byte $00,$00,$00,$AA,$4A,$A6,$A2,$0C ; 7BE0
.byte $00,$00,$04,$EE,$4E,$84,$EE,$00 ; 7BE8
.byte $40,$4E,$4C,$4E,$4A,$42,$42,$40 ; 7BF0
.byte $00,$28,$6C,$EE,$6C,$28,$00,$00 ; 7BF8
right_margin:
; Default value is 79 decimal. Unsure why the author didn't use RMARGN at $53
.byte $4F ; 7C00 4F
; ----------------------------------------------------------------------------
; Start of COL80 code.
; Callback for CIO OPEN command.
col80_open:
jsr init_graphics_8 ; 7C01 20 14 7C
lda #$00 ; 7C04 A9 00
sta ROWCRS ; 7C06 85 54
sta COLCRS ; 7C08 85 55
nop ; 7C0A EA
nop ; 7C0B EA
sta BUFCNT ; 7C0C 85 6B
lda #$4F ; 7C0E A9 4F
sta right_margin ; 7C10 8D 00 7C
rts ; 7C13 60
; ----------------------------------------------------------------------------
; Assembly version of GRAPHICS 8+16 command.
init_graphics_8:
lda #$08 ; 7C14 A9 08
sta ICAX2Z ; 7C16 85 2B
lda #$0C ; 7C18 A9 0C
sta ICAX1Z ; 7C1A 85 2A
jsr open_s_dev ; 7C1C 20 37 7C
; Set COL80's default colors
lda #$08 ; 7C1F A9 08
sta COLOR2 ; 7C21 8D C6 02
nop ; 7C24 EA
nop ; 7C25 EA
nop ; 7C26 EA
lda #$00 ; 7C27 A9 00
sta COLOR1 ; 7C29 8D C5 02
; Protect ourselves from BASIC and the OS
lda #<START_ADDRESS ; 7C2C A9 00
sta MEMTOP ; 7C2E 8D E5 02
lda #>START_ADDRESS ; 7C31 A9 7A
sta MEMTOP+1 ; 7C33 8D E6 02
rts ; 7C36 60
; ----------------------------------------------------------------------------
; Call the OPEN vector for the S: device, using the ROM vector table
; at $E410. The table stores address-minus-one of each routine, which is
; meant to actually be called via the RTS instruction (standard 6502
; technique, but confusing the first time you encounter it)
open_s_dev:
lda s_dev_open_hi ; 7C37 AD 11 E4
pha ; 7C3A 48
lda s_dev_open_lo ; 7C3B AD 10 E4
pha ; 7C3E 48
rts ; 7C3F 60
; ----------------------------------------------------------------------------
; Callback for CIO CLOSE command. Note that the routine does nothing, really
; (the OS will mark the E: device as being closed, but COL80 doesn't do any
; cleanup).
; The SPECIAL and GET STATUS callbacks in col80_vector_tab also point here.
col80_close:
jmp return_success
; ----------------------------------------------------------------------------
; Callback for the internal put-one-byte, used by the OS to implement the
; CIO PUT RECORD and PUT BYTES commands. This routine's one argument is
; the byte in the accumulator (the character to print).
; First, the routine checks for the cursor control characters it supports.
; COL80 only handles the EOL and clear-screen codes; trying to print
; backspaces, arrows, deletes, inserts, etc just causes their ATASCII
; graphics character to print instead.
col80_putbyte:
; EOL (decimal 155)?
cmp #$9B ; 7C43 C9 9B
bne check_clear ; 7C45 D0 08
lda right_margin ; 7C47 AD 00 7C
sta COLCRS ; 7C4A 85 55
jmp skip_write ; 7C4C 4C 7C 7C
check_clear:
; Clear (decimal 125)?
cmp #$7D ; 7C4F C9 7D
bne regular_char ; 7C51 D0 03
jmp clear_screen ; 7C53 4C 0B 7D
; See if this is an inverse video char (code >= 128)
regular_char:
tax ; 7C56 AA
bpl not_inverse ; 7C57 10 07
lda #$FF ; 7C59 A9 FF
sta inverse_mask ; 7C5B 8D 49 7F
bne skip_ninv ; 7C5E D0 05
not_inverse:
lda #$00 ; 7C60 A9 00
sta inverse_mask ; 7C62 8D 49 7F
skip_ninv:
txa ; 7C65 8A
and #$7F ; 7C66 29 7F
sta TMPCHR ; 7C68 85 50
lda DINDEX ; 7C6A A5 57
cmp #$08 ; 7C6C C9 08
beq graphics_ok ; 7C6E F0 03
; If we're not in GRAPHICS 8 mode, reinitialize ourselves
jsr col80_open ; 7C70 20 01 7C
graphics_ok:
; Call the routines that actually print the character
jsr setup_font_ptr ; 7C73 20 C9 7C
jsr setup_screen_ptr ; 7C76 20 34 7D
jsr write_font_data ; 7C79 20 82 7D
skip_write:
; Move the cursor 1 space to the right. This will
; advance us to the next line if we're at the margin,
; and scroll the screen if needed
jsr advance_cursor ; 7C7C 20 EE 7C
check_ssflag:
; The OS keyboard interrupt handler will toggle SSFLAG (start/stop fla
; any time the user presses ctrl-1
lda SSFLAG ; 7C7F AD FF 02
bne check_ssflag ; 7C82 D0 FB
jmp return_success ; 7C84 4C 31 7D
; ----------------------------------------------------------------------------
; Scroll the screen up one line (8 scanlines). This has to move almost 8K of
; data, so it's noticeably slower than scrolling the GR.0 text screen.
scroll_screen:
lda SAVMSC ; 7C87 A5 58
sta screen_ptr_lo ; 7C89 85 CB
clc ; 7C8B 18
adc #$40 ; 7C8C 69 40
; font_ptr_lo is actually being used here as a second pointer into
; screen RAM, instead of its usual use as a pointer into the
; font_data table
sta font_ptr_lo ; 7C8E 85 CD
lda SAVMSC+1 ; 7C90 A5 59
sta screen_ptr_hi ; 7C92 85 CC
adc #$01 ; 7C94 69 01
sta font_ptr_hi ; 7C96 85 CE
ldx #$1D ; 7C98 A2 1D
ldy #$00 ; 7C9A A0 00
scroll_line_loop:
lda (font_ptr_lo),y ; 7C9C B1 CD
sta (screen_ptr_lo),y ; 7C9E 91 CB
dey ; 7CA0 88
bne scroll_line_loop ; 7CA1 D0 F9
inc font_ptr_hi ; 7CA3 E6 CE
inc screen_ptr_hi ; 7CA5 E6 CC
dex ; 7CA7 CA
bne scroll_line_loop ; 7CA8 D0 F2
blank_bottom_row:
lda SAVMSC ; 7CAA A5 58
clc ; 7CAC 18
adc #$C0 ; 7CAD 69 C0
sta screen_ptr_lo ; 7CAF 85 CB
lda SAVMSC+1 ; 7CB1 A5 59
adc #$1C ; 7CB3 69 1C
sta screen_ptr_hi ; 7CB5 85 CC
lda #$00 ; 7CB7 A9 00
tay ; 7CB9 A8
blank_loop:
sta (screen_ptr_lo),y ; 7CBA 91 CB
dey ; 7CBC 88
bne blank_loop ; 7CBD D0 FB
inc screen_ptr_hi ; 7CBF E6 CC
ldy #$40 ; 7CC1 A0 40
blank_tail:
sta (screen_ptr_lo),y ; 7CC3 91 CB
dey ; 7CC5 88
bpl blank_tail ; 7CC6 10 FB
rts ; 7CC8 60
; ----------------------------------------------------------------------------
; Set up font_ptr_lo/hi to point to the font_data bitmap for the character in
; TMPCHR. Also sets lo_nybble_flag to let the caller know whether the
; bitmap is in the upper or lower 4 bits of the bytes pointed to.
setup_font_ptr:
lda #$00 ; 7CC9 A9 00
sta font_ptr_hi ; 7CCB 85 CE
sta lo_nybble_flag ; 7CCD 8D 48 7F
lda TMPCHR ; 7CD0 A5 50
clc ; 7CD2 18
ror ; 7CD3 6A
bcc font_hi_nybble ; 7CD4 90 05
ldx #$FF ; 7CD6 A2 FF
stx lo_nybble_flag ; 7CD8 8E 48 7F
font_hi_nybble:
clc ; 7CDB 18
rol ; 7CDC 2A
rol ; 7CDD 2A
rol font_ptr_hi ; 7CDE 26 CE
rol ; 7CE0 2A
rol font_ptr_hi ; 7CE1 26 CE
adc #<font_data ; 7CE3 69 00
sta font_ptr_lo ; 7CE5 85 CD
lda #>font_data ; 7CE7 A9 7A
adc font_ptr_hi ; 7CE9 65 CE
sta font_ptr_hi ; 7CEB 85 CE
rts ; 7CED 60
; ----------------------------------------------------------------------------
; Move the cursor one space to the right (to the next line if at the margin,
; and scroll screen if on the last row)
advance_cursor:
inc COLCRS ; 7CEE E6 55
lda right_margin ; 7CF0 AD 00 7C
cmp COLCRS ; 7CF3 C5 55
bcs same_line ; 7CF5 B0 13
lda LMARGN ; 7CF7 A5 52
sta COLCRS ; 7CF9 85 55
lda ROWCRS ; 7CFB A5 54
; $17 is 25 decimal, one row below the lowest on the screen
cmp #$17 ; 7CFD C9 17
bcc no_scroll ; 7CFF 90 07
jsr scroll_screen ; 7D01 20 87 7C
; Move to row 24 after scrolling
lda #$16 ; 7D04 A9 16
sta ROWCRS ; 7D06 85 54
no_scroll:
inc ROWCRS ; 7D08 E6 54
same_line:
rts ; 7D0A 60
; ----------------------------------------------------------------------------
; Clear the screen by setting all screen RAM bytes to zero. Slow, but not
; as slow as scrolling.
clear_screen:
lda SAVMSC ; 7D0B A5 58
sta screen_ptr_lo ; 7D0D 85 CB
lda SAVMSC+1 ; 7D0F A5 59
sta screen_ptr_hi ; 7D11 85 CC
ldy #$00 ; 7D13 A0 00
ldx #$1D ; 7D15 A2 1D
lda #$00 ; 7D17 A9 00
cls_loop:
sta (screen_ptr_lo),y ; 7D19 91 CB
dey ; 7D1B 88
bne cls_loop ; 7D1C D0 FB
inc screen_ptr_hi ; 7D1E E6 CC
dex ; 7D20 CA
bne cls_loop ; 7D21 D0 F6
jsr blank_bottom_row ; 7D23 20 AA 7C
lda LMARGN ; 7D26 A5 52
sta COLCRS ; 7D28 85 55
lda #$00 ; 7D2A A9 00
sta ROWCRS ; 7D2C 85 54
; redundant JMP
jmp return_success ; 7D2E 4C 31 7D
; ----------------------------------------------------------------------------
; CIO expects the Y register to contain a status code.
; 1 means success (no error). Lots of COL80's routines
; jump here.
return_success:
ldy #$01 ; 7D31 A0 01
rts ; 7D33 60
; ----------------------------------------------------------------------------
; Set screen_ptr_lo/hi to point to the address of the first byte of graphics
; data at the current cursor position.
setup_screen_ptr:
ldy ROWCRS ; 7D34 A4 54
lda SAVMSC ; 7D36 A5 58
clc ; 7D38 18
adc row_low_offset_tab,y ; 7D39 79 52 7D
sta screen_ptr_lo ; 7D3C 85 CB
lda SAVMSC+1 ; 7D3E A5 59
adc row_high_offset_tab,y ; 7D40 79 6A 7D
sta screen_ptr_hi ; 7D43 85 CC
lda COLCRS ; 7D45 A5 55
lsr ; 7D47 4A
clc ; 7D48 18
adc screen_ptr_lo ; 7D49 65 CB
bcc hi_byte_ok ; 7D4B 90 02
inc screen_ptr_hi ; 7D4D E6 CC
hi_byte_ok:
sta screen_ptr_lo ; 7D4F 85 CB
rts ; 7D51 60
; ----------------------------------------------------------------------------
; Tables of offsets for setup_screen_ptr, to avoid doing multiplication at
; runtime (the 6502 lacks a MUL instruction, so it's slow...)
row_low_offset_tab:
.byte $00,$40,$80,$C0,$00,$40,$80,$C0 ; 7D52
.byte $00,$40,$80,$C0,$00,$40,$80,$C0 ; 7D5A
.byte $00,$40,$80,$C0,$00,$40,$80,$C0 ; 7D62
row_high_offset_tab:
.byte $00,$01,$02,$03,$05,$06,$07,$08 ; 7D6A
.byte $0A,$0B,$0C,$0D,$0F,$10,$11,$12 ; 7D72
.byte $14,$15,$16,$17,$19,$1A,$1B,$1C ; 7D7A
; ----------------------------------------------------------------------------
; Copy pixel data from the font table to screen RAM.
; font_ptr_lo/hi must point to the correct character, and screen_ptr_lo/hi
; must point to the correct screen address for the current cursor position.
; This routine has separate execution paths for even- and odd-numbered
; cursor positions, since each byte of screen RAM holds data for two
; adjacent characters (and when printing to one of them, the other needs
; to be left undisturbed!)
write_font_data:
lda COLCRS ; 7D82 A5 55
clc ; 7D84 18
ror ; 7D85 6A
bcc write_font_data_even ; 7D86 90 31
ldx #$00 ; 7D88 A2 00
ldy #$00 ; 7D8A A0 00
get_font_nybble_odd:
lda (font_ptr_lo),y ; 7D8C B1 CD
bit lo_nybble_flag ; 7D8E 2C 48 7F
bne lo_nybble_odd ; 7D91 D0 04
; glyph we want is stored in top 4 bits of font byte,
; shift it down to the bottom 4 bits
lsr ; 7D93 4A
lsr ; 7D94 4A
lsr ; 7D95 4A
lsr ; 7D96 4A
lo_nybble_odd:
eor inverse_mask ; 7D97 4D 49 7F
and #$0F ; 7D9A 29 0F
sta TMPCHR ; 7D9C 85 50
ldy scanline_offset_tab,x ; 7D9E BC EA 7D
lda (screen_ptr_lo),y ; 7DA1 B1 CB
and #$F0 ; 7DA3 29 F0
ora TMPCHR ; 7DA5 05 50
sta (screen_ptr_lo),y ; 7DA7 91 CB
inx ; 7DA9 E8
cpx #$07 ; 7DAA E0 07
bne screen_ptr_ok_odd ; 7DAC D0 02
inc screen_ptr_hi ; 7DAE E6 CC
screen_ptr_ok_odd:
cpx #$08 ; 7DB0 E0 08
beq write_font_done_odd ; 7DB2 F0 04
txa ; 7DB4 8A
tay ; 7DB5 A8
bne get_font_nybble_odd ; 7DB6 D0 D4
write_font_done_odd:
rts ; 7DB8 60
; ----------------------------------------------------------------------------
; Write data to even-numbered columns, very similar to the above
write_font_data_even:
ldx #$00 ; 7DB9 A2 00
ldy #$00 ; 7DBB A0 00
get_font_nybble_even:
lda (font_ptr_lo),y ; 7DBD B1 CD
bit lo_nybble_flag ; 7DBF 2C 48 7F
beq hi_nybble_even ; 7DC2 F0 04
asl ; 7DC4 0A
asl ; 7DC5 0A
asl ; 7DC6 0A
asl ; 7DC7 0A
hi_nybble_even:
eor inverse_mask ; 7DC8 4D 49 7F
and #$F0 ; 7DCB 29 F0
sta TMPCHR ; 7DCD 85 50
ldy scanline_offset_tab,x ; 7DCF BC EA 7D
lda (screen_ptr_lo),y ; 7DD2 B1 CB
and #$0F ; 7DD4 29 0F
ora TMPCHR ; 7DD6 05 50
sta (screen_ptr_lo),y ; 7DD8 91 CB
inx ; 7DDA E8
cpx #$07 ; 7DDB E0 07
bne screen_ptr_ok_even ; 7DDD D0 02
inc screen_ptr_hi ; 7DDF E6 CC
screen_ptr_ok_even:
cpx #$08 ; 7DE1 E0 08
beq write_font_done_even ; 7DE3 F0 04
txa ; 7DE5 8A
tay ; 7DE6 A8
bne get_font_nybble_even ; 7DE7 D0 D4
write_font_done_even:
rts ; 7DE9 60
; ----------------------------------------------------------------------------
scanline_offset_tab:
.byte $00,$28,$50,$78,$A0,$C8,$F0,$18 ; 7DEA
; ----------------------------------------------------------------------------
; Callback for the internal get-one-byte, used by the OS to implement the
; CIO GET RECORD and GET BYTES commands. This routine takes no arguments,
; and returns the read byte in the accumulator.
; Internally, COL80 maintains a line buffer. Each time col80_getbyte is
; called, it returns the next character in the buffer. If the buffer's
; empty (or if the last call returned the last character), a new line
; of input is read from the user (and the first character is returned).
; This is exactly how the OS E: device works.
col80_getbyte:
lda BUFCNT ; 7DF2 A5 6B
beq get_line ; 7DF4 F0 0E
get_next_byte:
ldx line_buffer_index ; 7DF6 AE 4A 7F
lda line_buffer,x ; 7DF9 BD 4B 7F
dec BUFCNT ; 7DFC C6 6B
inc line_buffer_index ; 7DFE EE 4A 7F
jmp return_success ; 7E01 4C 31 7D
; ----------------------------------------------------------------------------
; Get a line of input from the user, terminated by the Return key.
get_line:
lda #$00 ; 7E04 A9 00
sta BUFCNT ; 7E06 85 6B
sta line_buffer_index ; 7E08 8D 4A 7F
show_cursor:
lda #$20 ; 7E0B A9 20
sta TMPCHR ; 7E0D 85 50
lda #$FF ; 7E0F A9 FF
sta inverse_mask ; 7E11 8D 49 7F
jsr setup_font_ptr ; 7E14 20 C9 7C
jsr setup_screen_ptr ; 7E17 20 34 7D
jsr write_font_data ; 7E1A 20 82 7D
jsr get_keystroke ; 7E1D 20 B7 7E
cpy #$01 ; 7E20 C0 01
beq keystroke_ok ; 7E22 F0 07
ldy #$00 ; 7E24 A0 00
sty line_buffer_index ; 7E26 8C 4A 7F
sty BUFCNT ; 7E29 84 6B
keystroke_ok:
cmp #$9B ; 7E2B C9 9B
bne check_backs_key ; 7E2D D0 03
jmp return_key_hit ; 7E2F 4C 52 7E
check_backs_key:
cmp #$7E ; 7E32 C9 7E
bne check_clear_key ; 7E34 D0 03
jmp backs_key_hit ; 7E36 4C 71 7E
check_clear_key:
cmp #$7D ; 7E39 C9 7D
bne normal_key_hit ; 7E3B D0 03
jmp clear_key_hit ; 7E3D 4C 64 7E
normal_key_hit:
ldx BUFCNT ; 7E40 A6 6B
bpl buffer_character ; 7E42 10 03
jmp beep ; 7E44 4C 8F 7E
buffer_character:
sta line_buffer,x ; 7E47 9D 4B 7F
jsr col80_putbyte ; 7E4A 20 43 7C
inc BUFCNT ; 7E4D E6 6B
jmp show_cursor ; 7E4F 4C 0B 7E
return_key_hit:
jsr print_space ; 7E52 20 A4 7E
lda #$9B ; 7E55 A9 9B
ldx BUFCNT ; 7E57 A6 6B
sta line_buffer,x ; 7E59 9D 4B 7F
inc BUFCNT ; 7E5C E6 6B
jsr col80_putbyte ; 7E5E 20 43 7C
jmp get_next_byte ; 7E61 4C F6 7D
clear_key_hit:
jsr clear_screen ; 7E64 20 0B 7D
lda #$00 ; 7E67 A9 00
sta line_buffer_index ; 7E69 8D 4A 7F
sta BUFCNT ; 7E6C 85 6B
jmp get_line ; 7E6E 4C 04 7E
backs_key_hit:
jsr print_space ; 7E71 20 A4 7E
lda BUFCNT ; 7E74 A5 6B
beq backs_key_done ; 7E76 F0 14
dec COLCRS ; 7E78 C6 55
lda COLCRS ; 7E7A A5 55
clc ; 7E7C 18
adc #$01 ; 7E7D 69 01
cmp LMARGN ; 7E7F C5 52
bne backs_same_line ; 7E81 D0 07
lda right_margin ; 7E83 AD 00 7C
sta COLCRS ; 7E86 85 55
dec ROWCRS ; 7E88 C6 54
backs_same_line:
dec BUFCNT ; 7E8A C6 6B
backs_key_done:
jmp show_cursor ; 7E8C 4C 0B 7E
; ----------------------------------------------------------------------------
; Ring the margin bell. COL80 doesn't implement the ctrl-2 bell (character
; 253), and instead of using the GTIA keyclick speaker, it uses POKEY to
; make a beep
beep: ldy #$00 ; 7E8F A0 00
ldx #$AF ; 7E91 A2 AF
beep_delay_x:
stx AUDF1 ; 7E93 8E 00 D2
stx AUDC1 ; 7E96 8E 01 D2
beep_delay_y:
dey ; 7E99 88
bne beep_delay_y ; 7E9A D0 FD
dex ; 7E9C CA
cpx #$9F ; 7E9D E0 9F
bne beep_delay_x ; 7E9F D0 F2
jmp show_cursor ; 7EA1 4C 0B 7E
; ----------------------------------------------------------------------------
; Print a space character at the current cursor position. Does not
; update the cursor position.
print_space:
lda #$00 ; 7EA4 A9 00
sta inverse_mask ; 7EA6 8D 49 7F
lda #$20 ; 7EA9 A9 20
sta TMPCHR ; 7EAB 85 50
jsr setup_font_ptr ; 7EAD 20 C9 7C
jsr setup_screen_ptr ; 7EB0 20 34 7D
jsr write_font_data ; 7EB3 20 82 7D
rts ; 7EB6 60
; ----------------------------------------------------------------------------
; Get a keystroke (blocking). Just calls the OS K: get-one-byte routine
; (call by pushing address-minus-one then doing an RTS)
get_keystroke:
lda k_dev_get_hi ; 7EB7 AD 25 E4
pha ; 7EBA 48
lda k_dev_get_lo ; 7EBB AD 24 E4
pha ; 7EBE 48
rts ; 7EBF 60
; ----------------------------------------------------------------------------
; Initialization callback. The OS will call this on coldstart (or would do,
; if the driver were in ROM), and also on warmstart (because we stole the
; DOSINI vector).
; This routine is also the first thing that gets called by the mainline
; init code. Its job is to install COL80 in the handler table at HATABS.
; Actually the handler is first installed as X:, then the main init code
; fixes this up to E: unless the user is holding down SELECT. This allows
; the user to toggle between the 40-column ROM E: and COL80 without doing
; a full reboot. No idea if this was a documented feature or something the
; author used for development/debugging.
col80_init:
ldy #$00 ; 7EC0 A0 00
next_hatab_slot:
lda HATABS,y ; 7EC2 B9 1A 03
beq register_x_handler ; 7EC5 F0 0A
iny ; 7EC7 C8
iny ; 7EC8 C8
iny ; 7EC9 C8
cpy #$20 ; 7ECA C0 20
bcc next_hatab_slot ; 7ECC 90 F4
jmp return_success ; 7ECE 4C 31 7D
register_x_handler:
lda #$58 ; 7ED1 A9 58
sta HATABS,y ; 7ED3 99 1A 03
lda #<col80_vector_tab ; 7ED6 A9 E5
iny ; 7ED8 C8
sta HATABS,y ; 7ED9 99 1A 03
lda #>col80_vector_tab ; 7EDC A9 7E
iny ; 7EDE C8
sta HATABS,y ; 7EDF 99 1A 03
jmp return_success ; 7EE2 4C 31 7D
; ----------------------------------------------------------------------------
; COL80 vector table, in the format required by the OS. Our HATABS entry
; will point to this table, and the OS will call the routines listed here
; via the "call by RTS" method (which is why they're address-minus-one).
; See the entry on HATABS in "Mapping the Atari" or the OS manual.
col80_vector_tab:
.word col80_open-1 ; 7EE5 00 7C
.word col80_close-1 ; 7EE7 3F 7C
.word col80_getbyte-1 ; 7EE9 F1 7D
.word col80_putbyte-1 ; 7EEB 42 7C
.word col80_close-1 ; 7EED 3F 7C
.word col80_close-1 ; 7EEF 3F 7C
jmp col80_init ; 7EF1 4C C0 7E
; ----------------------------------------------------------------------------
; The OS jumps here on warmstart (also, this is the run address in our
; binary load file)
dosini_entry_point:
nop ; 7EF4 EA
nop ; 7EF5 EA
nop ; 7EF6 EA
main_entry_point:
jsr col80_init ; 7EF7 20 C0 7E
lda CONSOL ; 7EFA AD 1F D0
and #$04 ; 7EFD 29 04
beq no_e_handler ; 7EFF F0 2F
lda #$0C ; 7F01 A9 0C
sta ICCOM ; 7F03 8D 42 03
ldx #$00 ; 7F06 A2 00
jsr CIOV ; 7F08 20 56 E4
lda #$58 ; 7F0B A9 58
sta font_ptr_lo ; 7F0D 85 CD
lda #$03 ; 7F0F A9 03
sta ICCOM ; 7F11 8D 42 03
lda #$CD ; 7F14 A9 CD
sta ICBAL ; 7F16 8D 44 03
lda #$00 ; 7F19 A9 00
sta ICBAH ; 7F1B 8D 45 03
ldx #$00 ; 7F1E A2 00
jsr CIOV ; 7F20 20 56 E4
ldy #$07 ; 7F23 A0 07
lda #<col80_vector_tab ; 7F25 A9 E5
sta HATABS,y ; 7F27 99 1A 03
lda #>col80_vector_tab ; 7F2A A9 7E
iny ; 7F2C C8
sta HATABS,y ; 7F2D 99 1A 03
no_e_handler:
lda #<START_ADDRESS ; 7F30 A9 00
sta MEMTOP ; 7F32 8D E5 02
lda #>START_ADDRESS ; 7F35 A9 7A
sta MEMTOP+1 ; 7F37 8D E6 02
jmp return_success ; 7F3A 4C 31 7D
; ----------------------------------------------------------------------------
; (when does this actually get called? da65 can't find any references
; to it, and it's not a run or init address in the binary load file)
lda #<dosini_entry_point ; 7F3D A9 F4
sta DOSINI ; 7F3F 85 0C
lda #>dosini_entry_point ; 7F41 A9 7E
sta DOSINI+1 ; 7F43 85 0D
jmp main_entry_point ; 7F45 4C F7 7E
; ----------------------------------------------------------------------------
; Various bits of runtime state here. It's unclear to me why the standard
; OS buffer location couldn't have been used instead (normally the top
; half of page 5), or why the other stuff couldn't have been stored in
; zero page, in locations used by the ROM E: handler (thus unused when
; it's replaced with COL80). line_buffer_index needs to be preserved
; across calls to col80_getbyte, but lo_nybble_flag and inverse_mask are
; freshly calculated every time they're used, so they could be almost
; anywhere.
lo_nybble_flag:
.byte $00 ; 7F48 00
inverse_mask:
.byte $00 ; 7F49 00
line_buffer_index:
.byte $12 ; 7F4A 12
; ----------------------------------------------------------------------------
; There's absolutely no reason why this data needs to be included in the
; binary load file: the line buffer's initial contents are meaningless, they
; will be blown away the first time anything reads from the E: device.
; Notice the author was running his debugger in COL80 when he built the
; binary (ASCII "S COL80 7A00 7F80" command still in the buffer).
line_buffer:
.byte $53,$20,$43,$4F,$4C,$38,$30,$20 ; 7F4B
.byte $37,$41,$30,$30,$20,$37,$46,$38 ; 7F53
.byte $30,$9B,$20,$20,$20,$20,$9B,$27 ; 7F5B
.byte $40,$40,$40,$40,$28,$28,$28,$28 ; 7F63
.byte $40,$40,$40,$40,$40,$40,$40,$40 ; 7F6B
.byte $40,$40,$40,$40,$40,$40,$40,$40 ; 7F73
.byte $9B,$FD,$FD,$FD,$FD,$9B ; 7F7B
END_ADDRESS = *-1
; I've found a variant (modified version?) of this code, that doesn't
; include the line_buffer in the file (no reason for it to be there),
; or the $0C segment, and that has another segment, loaded at $6000,
; with the run address changed to $6000. The code looks like:
; .org $6000
; jsr dosini_entry_point
; lda #$50
; sta RMARGN
; lda #$00
; sta COLOR2
; also, the default colors have been changed in init_graphics_8.
; There are at least two binaries floating around that contain
; extra (garbage) bytes at the end, presumably from being transferred
; over XMODEM or similar. They are otherwise identical.
|
