Applecorn/auxmem.init.s
2021-10-24 20:38:32 -04:00

200 lines
6.3 KiB
ArmAsm

* AUXMEM.INIT.S
* (c) Bobbi 2021 GPL v3
*
* Initialization code running in Apple //e aux memory
***********************************************************
* BBC Micro 'virtual machine' in Apple //e aux memory
***********************************************************
ZP1 EQU $90 ; $90-$9f are spare Econet space
; so safe to use
ZP2 EQU $92
ZP3 EQU $94
STRTBCKL EQU $9D ; *TO DO* don't need to preserve
STRTBCKH EQU $9E
MOSSHIM
ORG AUXMOS ; MOS shim implementation
*
* Shim code to service Acorn MOS entry points using
* Apple II monitor routines
* This code is initially loaded into aux mem at AUXMOS1
* Then relocated into aux LC at AUXMOS by MOSINIT
*
* Initially executing at $3000 until copied to $D000
MOSINIT LDX #$FF ; Initialize Alt SP to $1FF
TXS
STA $C005 ; Make sure we are writing aux
STA $C000 ; Make sure 80STORE is off
LDA $C08B ; LC RAM Rd/Wt, 1st 4K bank
LDA $C08B
:MODBRA BRA :RELOC ; NOPped out on first run
BRA :NORELOC
LDA #$EA ; NOP opcode
STA :MODBRA
STA :MODBRA+1
:RELOC LDA #<AUXMOS1 ; Relocate MOS shim
STA A1L
LDA #>AUXMOS1
STA A1H
LDA #<EAUXMOS1
STA A2L
LDA #>EAUXMOS1
STA A2H
LDA #<AUXMOS
STA A4L
LDA #>AUXMOS
STA A4H
:L1 LDA (A1L)
STA (A4L)
LDA A1H
CMP A2H
BNE :S1
LDA A1L
CMP A2L
BNE :S1
BRA :S4
:S1 INC A1L
BNE :S2
INC A1H
:S2 INC A4L
BNE :S3
INC A4H
:S3 BRA :L1
:S4 LDA #<MOSVEC-MOSINIT+AUXMOS1
STA A1L
LDA #>MOSVEC-MOSINIT+AUXMOS1
STA A1H
LDA #<MOSVEND-MOSINIT+AUXMOS1
STA A2L
LDA #>MOSVEND-MOSINIT+AUXMOS1
STA A2H
LDA #<MOSAPI
STA A4L
LDA #>MOSAPI
STA A4H
:L2 LDA (A1L)
STA (A4L)
LDA A1H
CMP A2H
BNE :S5
LDA A1L
CMP A2L
BNE :S5
BRA :S8
:S5 INC A1L
BNE :S6
INC A1H
:S6 INC A4L
BNE :S7
INC A4H
:S7 BRA :L2
:NORELOC
:S8 STA $C00D ; 80 col on
STA $C003 ; Alt charset off
STA $C055 ; PAGE2
JMP MOSHIGH ; Ensure executing in high memory here
MOSHIGH SEI
LDX #$FF
TXS ; Initialise stack
INX ; X=$00
TXA
:SCLR STA $0000,X ; Clear Kernel memory
STA $0200,X
STA $0300,X
INX
BNE :SCLR
LDX #ENDVEC-DEFVEC-1
:INITPG2 LDA DEFVEC,X ; Set up vectors
STA $200,X
DEX
BPL :INITPG2
JSR INITROMS ; Initialize sideways ROM table
JSR KBDINIT ; Returns A=startup MODE
JSR VDUINIT ; Initialise VDU driver
JSR PRHELLO
LDA #7
JSR OSWRCH
JSR OSNEWL
LDX MAXROM ; TEMP X=language to enter
CLC
* OSBYTE $8E - Enter language ROM
* X=ROM number to select
*
BYTE8E PHP ; Save CLC=RESET, SEC=Not RESET
JSR ROMSELECT ; Bring ROM X into memory
STX BYTEVARBASE+$FC ; Set current language ROM
LDA #$00
STA FAULT+0
LDA #$80
STA FAULT+1
LDY #$09
JSR PRERRLP ; Print ROM name with PRERR to set
STY FAULT+0 ; FAULT pointing to version string
JSR OSNEWL
JSR OSNEWL
PLP ; Get entry type back
LDA #$01
JMP AUXADDR
* OSBYTE $8F - Issue service call
* X=service call, Y=parameter
*
SERVICE TAX ; Enter here with A=Service Num
BYTE8F
SERVICEX LDA $F4
PHA ; Save current ROM
TXA
LDX MAXROM ; Start at highest ROM
:SERVLP JSR ROMSELECT ; Bring it into memory
BIT $8006
BPL :SERVSKIP ; No service entry
JSR $8003 ; Call service entry
TAX
BEQ :SERVDONE
:SERVSKIP LDX $F4 ; Restore X=current ROM
DEX ; Step down to next
BPL :SERVLP ; Loop until ROM 0 done
:SERVDONE PLA ; Get caller's ROM back
PHX ; Save return from service call
TAX
JSR ROMSELECT ; Restore caller's ROM
PLX ; Get return value back
TXA ; Return in A and X and set EQ/NE
RTS
PRHELLO LDA #<HELLO
LDY #>HELLO
JSR PRSTR
JMP OSNEWL
BYTE00XX
BYTE00 BEQ BYTE00A ; OSBYTE 0,0 - generate error
LDX #$0A ; Identify Host
RTS ; %000x1xxx host type, 'A'pple
BYTE00A BRK
DB $F7
HELLO ASC 'Applecorn MOS 2021-10-24'
DB $00 ; Unify MOS messages