Applecorn/auxmem.init.s
2021-08-26 17:36:46 -04:00

153 lines
4.4 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 Econet space
; so safe to use
ZP2 EQU $92
ZP3 EQU $94
* COL,ROW needs to be in X,Y order
* TO DO: will be moved to VDU space
COL EQU $96 ; Cursor column
ROW EQU $97 ; Cursor row
STRTBCKL EQU $9D
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 KBDINIT ; Returns A=startup MODE
JSR VDUINIT ; Initialise VDU driver
JSR PRHELLO
LDA #7
JSR OSWRCH
JSR OSNEWL
CLC
JMP BYTE8E
PRHELLO LDA #<HELLO
LDY #>HELLO
JSR PRSTR
JMP OSNEWL
BYTE00XX BEQ BYTE00A ; OSBYTE 0,0 - generate error
LDX #$0A ; $00 = identify Host
RTS ; %000x1xxx host type, 'A'pple
BYTE00A BRK
DB $F7
HELLO ASC 'Applecorn MOS v0.01'
DB $00 ; Unify MOS messages