Applecorn/mainmem.init.s
2021-09-21 22:59:11 -04:00

115 lines
2.7 KiB
ArmAsm

* MAINMEM.INIT.S
* (c) Bobbi 2021 GPLv3
*
* Initialization, interrupt handling and reset handling code
* that resides in main memory.
* Trampoline in main memory used by aux memory IRQ handler
* to invoke Apple II / ProDOS IRQs in main memory
A2IRQ >>> IENTMAIN ; IENTMAIN does not do CLI
JSR A2IRQ2
>>> XF2AUX,IRQBRKRET
A2IRQ2 PHP ; Fake things to look like IRQ
JMP (A2IRQV) ; Call Apple II ProDOS ISR
* BRK handler in main memory. Used on Apple IIgs only.
GSBRK >>> XF2AUX,GSBRKAUX
* Set prefix if not already set
SETPRFX LDA #GPFXCMD
STA :OPC7 ; Initialize cmd byte to $C7
:L1 JSR MLI
:OPC7 DB $00
DW GSPFXPL
LDX DRVBUF1 ; was $0300
BNE RTSINST
LDA $BF30
STA ONLNPL+1 ; Device number
JSR MLI
DB ONLNCMD
DW ONLNPL
LDA DRVBUF2 ; was $0301
AND #$0F
TAX
INX
STX DRVBUF1 ; was $0300
LDA #'/'
STA DRVBUF2 ; was $0301
DEC :OPC7
BNE :L1
RTSINST RTS
* Disconnect /RAM ramdrive to avoid aux corruption
* Stolen from Beagle Bros Extra K
DISCONN LDA $BF98
AND #$30
CMP #$30
BNE :S1
LDA $BF26
CMP $BF10
BNE :S2
LDA $BF27
CMP $BF11
BEQ :S1
:S2 LDY $BF31
:L1 LDA $BF32,Y
AND #$F3
CMP #$B3
BEQ :S3
DEY
BPL :L1
BMI :S1
:S3 LDA $BF32,Y
STA DRVBUF2+1 ; was $0302
:L2 LDA $BF33,Y
STA $BF32,Y
BEQ :S4
INY
BNE :L2
:S4 LDA $BF26
STA DRVBUF1 ; was $0300
LDA $BF27
STA DRVBUF2 ; was $0301
LDA $BF10
STA $BF26
LDA $BF11
STA $BF27
DEC $BF31
:S1 RTS
* Reset handler - invoked on Ctrl-Reset
* XFER to AUXMOS ($C000) in aux, AuxZP on, LC on
RESET TSX
STX $0100
LDA $C058 ; AN0 off
LDA $C05A ; AN1 off
LDA $C05D ; AN2 on
LDA $C05F ; AN3 on
LDA #$20 ; PAGE2 shadow on ROM3 GS
TRB $C035
>>> XF2AUX,AUXMOS
RTS