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Applecorn
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Implemented MODE 0/1 reverse scrolling.

This commit is contained in:
Bobbi Webber-Manners 2022-12-29 01:04:49 -05:00
parent f83c7ee8f1
commit d503afae43
2 changed files with 71 additions and 3 deletions
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applecorn.po
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74
auxmem.shr.s
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@ -431,7 +431,7 @@ SHRPRCH640 SEC
* Apply colour masks to 16 bit word of character data
* Called in 6816 native mode, 16 bit
* Called in 65816 native mode, 16 bit
MX %00 ; Tell Merlin 16 bit M & X
SHRCOLWORD
PHA ; Keep A
@ -553,8 +553,76 @@ SHRSCR1LINE PHY
* Reverse scroll one line
* Copy text line A to line A+1
* TODO: Implement this
SHRRSCR1LINE
SHRRSCR1LINE PHY
PHX
STA VDUADDR+1 ; Screen line -> MSB
STZ VDUADDR+0 ; Zero LSB
PHP ; Disable interrupts
SEI
CLC ; Enter native mode
XCE
PHB ; Preserve data bank
REP #$31 ; M,X 16 bit, carry clear
MX %00 ; Tell Merlin
LDA VDUADDR ; Screen line to scroll
ASL ; Mult 4
ASL
ADC VDUADDR ; Mult 5
STA VDUADDR ; VDUADDR = line * $500
LDA TXTWINLFT ; Left margin
LDY VDUPIXELS ; Pixels per byte
CPY #$02 ; 2 pixels per byte in 320 mode
BNE :S1
ASL ; Double TXTWINLFT
:S1 ASL ; 2 bytes / char
AND #$00ff ; Mask to get 8 bit result
ADC VDUADDR ; Add to beginning of line addr
STA VDUADDR ; VDUADDR = start position
SEP #$21 ; M 8 bit, X 16 bit, carry set
MX %10 ; Tell Merlin
LDA TXTWINRGT ; Compute width ..
SBC TXTWINLFT ; .. right minus left
LDY VDUPIXELS ; Pixels per byte
CPY #$02 ; 2 pixels per byte in 320 mode
BNE :S2
ASL ; Double the width for 320
INC A ; Plus one
:S2 REP #$31 ; M,X 16 bit, carry clear
MX %00 ; Tell Merlin
ASL ; 2 bytes / char
AND #$00ff ; Mask to get 8 bit result
ADC VDUADDR ; Add to start position
TAX ; Will use as index
PEA #$E1E1 ; Set databank to $E1
PLB
PLB
:LOOP1 LDA $2000,X ; 2 bytes, row 0
STA $2500,X
LDA $20A0,X ; row 1
STA $25A0,X
LDA $2140,X ; row 2
STA $2640,X
LDA $21E0,X ; row 3
STA $26E0,X
LDA $2280,X ; row 4
STA $2780,X
LDA $2320,X ; row 5
STA $2820,X
LDA $23C0,X ; row 6
STA $28C0,X
LDA $2460,X ; row 7
STA $2960,X
DEX ; Update index
DEX
BMI :DONE ; Jump out if odd->-ve
CPX VDUADDR ; Compare with start addr
BCS :LOOP1 ; Bytes left? Go again
:DONE PLB ; Recover data bank
SEC ; Back to emulation mode
XCE
PLP ; Recover flags + regs
PLX
PLY
RTS