Applecorn/applecorn.s
Bobbi Webber-Manners 9552ae0d29 More code cleanup
2021-07-31 18:58:59 -04:00

140 lines
3.4 KiB
ArmAsm

* Load an Acorn BBC Micro ROM in aux memory and
* Provide an environment where it can run
* (c) Bobbi 2021 GPLv3
*
* Assembled with the Merlin 8 assembler.
XC ; 65c02
ORG $2000 ; Load addr of loader in main memory
* Monitor routines
BELL EQU $FBDD
PRBYTE EQU $FDDA
COUT1 EQU $FDED
CROUT EQU $FD8E
AUXMOVE EQU $C311
XFER EQU $C314
* Monitor ZP locations
A1L EQU $3C
A1H EQU $3D
A2L EQU $3E
A2H EQU $3F
A4L EQU $42
A4H EQU $43
* Used by XFER
STRTL EQU $3ED
STRTH EQU $3EE
* Reset vector (2 bytes + 1 byte checksum)
RSTV EQU $3F2
* MLI entry point
MLI EQU $BF00
* ProDOS MLI command numbers
QUITCMD EQU $65
GTIMECMD EQU $82
CREATCMD EQU $C0
DESTCMD EQU $C1
ONLNCMD EQU $C5
SPFXCMD EQU $C6
GPFXCMD EQU $C7
OPENCMD EQU $C8
READCMD EQU $CA
WRITECMD EQU $CB
CLSCMD EQU $CC
FLSHCMD EQU $CD
GMARKCMD EQU $CF
GEOFCMD EQU $D1
* IO Buffer for reading file (1024 bytes)
IOBUF0 EQU $4000 ; For loading ROM, OSFILE, *.
IOBUF1 EQU $4400 ; Four open files for langs
IOBUF2 EQU $4800
IOBUF3 EQU $4C00
IOBUF4 EQU $5000
* 512 byte buffer sufficient for one disk block
BLKBUF EQU $5200
BLKBUFEND EQU $5400
* Address in aux memory where ROM will be loaded
AUXADDR EQU $8000
* Address in aux memory where the MOS shim is located
AUXMOS1 EQU $2000 ; Temp staging area in Aux
EAUXMOS1 EQU $3000 ; End of staging area
AUXMOS EQU $D000 ; Final location in aux LC
* Macro for calls from main memory to aux memory
XFAUX MAC
SEC ; Use aux memory
BIT $FF58 ; Set V: use alt ZP and LC
JMP XFER
EOM
* Macro for calls from aux memory to main memory
XFMAIN MAC
CLC ; Use main memory
CLV ; Use main ZP and LC
JMP XFER
EOM
* Macro to load addr into STRTL/STRTH
* Called by code running in main mem
XFADDR MAC
PHA
LDA $C08B ; R/W LC RAM, bank 1
LDA $C08B
LDA #<]1
STA STRTL
LDA #>]1
STA STRTH
PLA
EOM
* Macro to backup STRTL/STRTH then load XFADDR
* Called by code running in aux mem
XFADDRAUX MAC
PHA
LDA STRTL
STA STRTBCKL
LDA STRTH
STA STRTBCKH
LDA #<]1
STA STRTL
LDA #>]1
STA STRTH
PLA
EOM
* Macro called on re-entry to aux memory
ENTAUX MAC
LDX $0101 ; Recover alt SP
TXS
PHA
LDA STRTBCKL
STA STRTL
LDA STRTBCKH
STA STRTH
PLA
EOM
* Macro called on re-entry to main memory
ENTMAIN MAC
LDX $0100 ; Recover SP
TXS
PHA ; Preserve parm in A
LDA $C081 ; Bank in ROM
LDA $C081
PLA
EOM
* Code is all included from PUT files below ...
PUT LOADER
PUT MAINMEM
PUT AUXMEM