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[putchar] Comments to putchar function, hypothesis on some variables #6

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96 changes: 57 additions & 39 deletions V1.01_ROM_disassembly_C000.asm
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Original file line number Diff line number Diff line change
Expand Up @@ -745,14 +745,14 @@ bios_putchar_c45e:
cp $07 ;[c4a9] jump if BEL
call z,$c5f4 ;[c4ab]
cp $00 ;[c4ae] jump if NUL
jp z,label_c6a3 ;[c4b0]
jp z,label_c6a3 ;[c4b0] ... aka the end, go to putchar epilogue
jp label_c4be ;[c4b3] jump if any other not printable character

; Handle ESC
; SUBROUTINE C4B6; putchar(ESC)
label_c4b6:
ld a,$01 ;[c4b6]
ld ($ffd8),a ;[c4b8]
jp label_c6a3 ;[c4bb]
ld ($ffd8),a ;[c4b8] *$ffd8 = 0x01
jp label_c6a3 ;[c4bb] the end, go to putchar epilogue

; Handle all, but special characters
label_c4be:
Expand Down Expand Up @@ -811,27 +811,31 @@ label_c510:
call $c71c ;[c51b]
call $c62e ;[c51e]
jp label_c6a3 ;[c521]

; SUBROUTINE C524; putchar(CR)
label_c524:
ld a,($ffd0) ;[c524]
ld ($ffca),a ;[c527]
ld a,($ffd0) ;[c524] load value of first column
ld ($ffca),a ;[c527] and update posx with it
ld c,a ;[c52a]
ld a,($ffcb) ;[c52b]
ld a,($ffcb) ;[c52b] load posy
ld b,a ;[c52e]
jp label_c5e5 ;[c52f]

; SUBROUTINE C532; putchar(LF)
label_c532:
ld a,($ffcb) ;[c532]
ld a,($ffcb) ;[c532] load cursor posy
ld b,a ;[c535]
ld a,($ffcd) ;[c536]
ld a,($ffcd) ;[c536] load max lines-1
cp b ;[c539]
jr z,label_c54b ;[c53a]
jr z,label_c54b ;[c53a] jump posy == last line
inc b ;[c53c]
ld a,b ;[c53d]
ld ($ffcb),a ;[c53e]
ld ($ffcb),a ;[c53e] update current posy
label_c541:
push iy ;[c541]
pop hl ;[c543]
pop hl ;[c543] hl <- iy
ld de,$0050 ;[c544]
add hl,de ;[c547]
add hl,de ;[c547] add 80 columns to character video memory pointer
jp label_c5e8 ;[c548]
label_c54b:
call $c62e ;[c54b]
Expand All @@ -840,24 +844,28 @@ label_c54b:
ld a,($ffca) ;[c552]
ld c,a ;[c555]
jr label_c541 ;[c556]

; SUBROUTINE C558; putchar(TAB)
label_c558:
ld a,($ffcb) ;[c558]
ld a,($ffcb) ;[c558] load posy
ld b,a ;[c55b]
ld a,($ffce) ;[c55c]
cp b ;[c55f]
jp z,label_c6a3 ;[c560]
ld a,($ffce) ;[c55c] load next tab stop position
cp b ;[c55f] if already in next tab stop position, do nothing
jp z,label_c6a3 ;[c560] the end, go to putchar epilogue
dec b ;[c563]
ld a,b ;[c564]
ld ($ffcb),a ;[c565]
ld ($ffcb),a ;[c565] update posx moving cursor to next tab stop
ld a,($ffca) ;[c568]
ld c,a ;[c56b]
jp label_c5e5 ;[c56c]

label_c56f:
call $c5f8 ;[c56f]
ld a,($ffcb) ;[c572]
ld b,a ;[c575]
jr c,label_c57b ;[c576]
jp label_c5e5 ;[c578]

label_c57b:
ld a,($ffd0) ;[c57b]
ld ($ffca),a ;[c57e]
Expand All @@ -876,23 +884,26 @@ label_c594:
call $c62e ;[c595]
pop bc ;[c598]
jr label_c5e5 ;[c599]

; SUBROUTINE C59B; putchar(Backspace)
label_c59b:
ld a,($ffca) ;[c59b]
ld a,($ffca) ;[c59b] load posx
ld c,a ;[c59e]
ld a,($ffd0) ;[c59f]
ld a,($ffd0) ;[c59f] load column 0 position
cp c ;[c5a2]
jr z,label_c5b8 ;[c5a3]
dec c ;[c5a5]
jr z,label_c5b8 ;[c5a3] jump if posx == first column
dec c ;[c5a5] move cursor backwards
ld a,($ffd1) ;[c5a6]
bit 3,a ;[c5a9]
jr z,label_c5ae ;[c5ab]
dec c ;[c5ad]
dec c ;[c5ad] if bit 3 of $ffd1 set, double cursor movement
label_c5ae:
ld a,c ;[c5ae]
ld ($ffca),a ;[c5af]
ld ($ffca),a ;[c5af] update posx
ld a,($ffcb) ;[c5b2]
ld b,a ;[c5b5]
ld b,a ;[c5b5] prepare posy in b
jr label_c5e5 ;[c5b6]

label_c5b8:
ld a,($ffcf) ;[c5b8]
ld b,a ;[c5bb]
Expand All @@ -913,21 +924,27 @@ label_c5c4:
ld a,b ;[c5d5]
ld ($ffcb),a ;[c5d6]
jr label_c5e5 ;[c5d9]

; SUBROUTINE C5DB; putchar(RS), go home cursor, you're drunk
label_c5db:
xor a ;[c5db]
ld ($ffcb),a ;[c5dc]
ld ($ffcb),a ;[c5dc] load 0 in posx, posy
ld ($ffca),a ;[c5df]
ld bc,$0000 ;[c5e2]
ld bc,$0000 ;[c5e2] prepare 0 in bc
label_c5e5:
call $c6f1 ;[c5e5]
label_c5e8:
call $c71c ;[c5e8]
jp label_c6a3 ;[c5eb]
jp label_c6a3 ;[c5eb] the end, go to putchar epilogue

; SUBROUTINE C5EE; putchar(SUB)
label_c5ee:
call $c764 ;[c5ee]
jp label_c6a3 ;[c5f1]
xor a ;[c5f4]
out ($da),a ;[c5f5]
jp label_c6a3 ;[c5f1] the end, go to putchar epilogue

; SUBROUTINE C5F4; putchar(BEL)
xor a ;[c5f4] Make buzzer beep...
out ($da),a ;[c5f5] ...if ASCII is not an opinion
ret ;[c5f7]

; SUBROUTINE 0xC5F8
Expand Down Expand Up @@ -1057,17 +1074,17 @@ label_c6a3:
inc hl ;[c6b8]
ld (hl),a ;[c6b9] *$ffcc = 0
inc hl ;[c6ba]
ld (hl),$17 ;[c6bb] *$ffce = "23" (rows(?)-1)
ld (hl),$17 ;[c6bb] *$ffcd = "23" (rows(?)-1)
inc hl ;[c6bd]
ld (hl),a ;[c6be] *$ffcf = 0
ld (hl),a ;[c6be] *$ffce = 0
inc hl ;[c6bf]
ld (hl),$4f ;[c6c0] *$ffd0 = "79" (columns-1)
ld (hl),$4f ;[c6c0] *$ffcf = "79" (columns-1)
inc hl ;[c6c2]
ld (hl),a ;[c6c3] *$ffd1 = 0
ld (hl),a ;[c6c3] *$ffd0 = 0
inc hl ;[c6c4]
ld (hl),a ;[c6c5] *$ffd2 = 0
ld (hl),a ;[c6c5] *$ffd1 = 0
inc hl ;[c6c6]
ld (hl),$80 ;[c6c7] *$ffd3 = 0
ld (hl),$80 ;[c6c7] *$ffd2 = 0
inc hl ;[c6c9]
ld a,($c86f) ;[c6ca] a <- cursor data raster from crtc_cfg, "$0d"
ld d,a ;[c6cd] d <- a
Expand All @@ -1081,12 +1098,12 @@ label_c6d6:
set 5,d ;[c6da]
set 6,d ;[c6dc]
label_c6de:
ld (hl),d ;[c6de] *$ffd4 value is not prior known
ld (hl),d ;[c6de] *$ffd3 value is not prior known
xor a ;[c6df] prepare registers for $c6e3 loop
inc hl ;[c6e0]
ld b,$15 ;[c6e1]
label_c6e3:
ld (hl),a ;[c6e3] write 0 in all memory in [$ffd5:$ffe9]
ld (hl),a ;[c6e3] write 0 in all memory in [$ffd4:$ffe8]
inc hl ;[c6e4]
djnz label_c6e3 ;[c6e5]
ret ;[c6e7]
Expand Down Expand Up @@ -1137,6 +1154,7 @@ label_c701:
ret ;[c71b]

; SUBROUTINE C71C; CRTC TODO; crtc_foo_c71c(hl: value, ix)
; Update cursor position in CRTC
crtc_foo_c71c:
ld a,h ;[c71c]
and $07 ;[c71d]
Expand Down