+ ;
+ ; bootstrap for ASCII 8kb mapped rom
+ ;
.area _BOOT
.db 'A'
.dw bootstrap
.dw 0,0,0,0,0,0
- .globl enaslt
- ; data to save from bios
- .globl _slotrom
- .globl _slotram
- .globl _vdpport
- .globl _infobits
- .globl _machine_type
+ .include "msx2.def"
.globl find_ram
- .globl kstack_top
-
+ .globl enaslt
; At this point the BIOS has detected the cartridge AB signature and
- ; jumped here; we have the rom bios in bank 0, ram in bank 3, and rom
- ; in bank 1 (this code).
+ ; jumped here; we have the rom bios in slot_page 0, ram in slot_page 3, and rom
+ ; in slot_page 1 (this code).
+ ;
+ ; Kernel is in mapped ROM pages 0x02 to 0x08, this code is in page 0x00
+ ; We just set RAM in slot_page 2 and copy over the kernel in chunks of 8K
+ ;
bootstrap:
di
ld sp,#0xf340 ; temporary stack
ld ix,#0x00d5
call #0x015f
- ; read slot registers from bios before overwritting them
+ ;
+ ; set ram in slot_page 2
+ ;
call find_ram
- ld hl,#0x8000
- call enaslt ; set bank 2 to ram
+ ld hl,#PAGE2_BASE
+ call enaslt
- ld a, #4
- out (0xFE),a
+ ld b,#3 ; starting ram page (copy to 3,2,1,4)
+ ld c,#2 ; starting rom page (copy from 2,3,4,5,6,7,8,9)
- call find_ram
- ld d,a
- call find_rom
- ld e,a
+nextrampage:
+ ld a, b
+ out (RAM_PAGE2),a
- ; read machine info bits
- ld bc,(0x002b) ; localization and interrupt frequency
- ld hl,(0x0006) ; vdp ports
- inc h
- inc l
- ld a,(0x002d) ; machine type
+ ld a,c
+ ld (ASCII8_ROM_PAGE1),a
- ex af,af'
- ld a,e
+ exx
+ ld hl, #ASCII8_PAGE1_BASE
+ ld de, #PAGE2_BASE
+ ld bc, #0x2000
+ ldir
exx
- ld hl,#0xc000
- ld sp,#0xa000 ; keep stack in ram
- call enaslt ; set bank 3 to rom
+ inc c
+ ld a,c
+ ld (ASCII8_ROM_PAGE1),a
- ; copy kernel page 0 from bank 3 to ram in bank 2
- ; it contains the common area if the rom > 48Kb
- ld hl, #0xc000
- ld de, #0x8000
- ld bc, #0x4000
+ exx
+ ld hl, #ASCII8_PAGE1_BASE
+ ld de, #PAGE2_BASE+0x2000
+ ld bc, #0x2000
ldir
-
exx
+
+ inc c
+ dec b
+ ld a,b
+ cp #3
+ jr z, done
+ or a
+ jr nz, nextrampage
+ ld b, #4
+ jr nextrampage
+done:
+ ;
+ ; Collect BIOS info bits and stash to ram
+ ;
+ call find_ram ; this requires ram page 0 in slot_page 3
+ ld d,a
+ call find_rom
+ ld e,a
+
+ ld a, #4
+ out (RAM_PAGE3),a
+
+ ld bc,(BIOS_VERSION1) ; localization and interrupt frequency
+ ld hl,(BIOS_VDP_IOPORT) ; vdp ports
+ inc h
+ inc l
+ ld a,(BIOS_MACHINE_TYPE) ; machine type
+ ld sp,#0xe100
push de
push bc
push hl
- ld hl,#0xc000 ; set bank 3 back to ram
- ld a,d
- call enaslt
- pop hl
- pop bc
- pop de
+ push af
- ld a, #4
- out (0xFF),a
+ ;
+ ; prepare for all-ram
+ ;
ld a,d
- ld (_slotram),a
- ld a,e
- ld (_slotrom),a
- ld (_infobits),bc
- ld (_vdpport),hl
- ex af,af'
- ld (_machine_type),a
-
- ld sp, #kstack_top ; move stack to final location
-
- ; set cartridge rom in bank 0
- ld a,e
- ld hl,#0
- call enaslt
-
- ; copy kernel page 3 to ram
- ld a, #3
- out (0xFE),a
- ld hl, #0x0
- ld de, #0x8000
- ld bc, #0x4000
- ldir
-
- ; set ram in bank 0 and cartridge rom in bank 2
- ld a,(_slotram)
- ld hl,#0
+ ld hl,#PAGE0_BASE
call enaslt
- ld a,(_slotrom)
- ld hl,#0x8000
- call enaslt
-
- ; copy kernel pages 2 and 1 to ram
- ld a, #2
- out (0xFC),a
- ld hl, #0x4000
- ld de, #0x0
- ld bc, #0x4000
- ldir
- ld a, #1
- out (0xFC),a
- ld hl, #0x8000
- ld de, #0x0
- ld bc, #0x4000
- ldir
- ; prepare mapped ram pages for all-ram
ld a, #3
- out (0xFC), a
+ out (RAM_PAGE0), a
ld a, #2
- out (0xFD), a
+ out (RAM_PAGE1), a
ld a, #1
- out (0xFE), a
- ld a, #4
- out (0xFF),a
-
- ; set bank 2 to ram
- ld a,(_slotram)
- ld hl,#0x8000
- call enaslt
+ out (RAM_PAGE2), a
; jump to start while keeping rom in page 1 (we are running from it)
; will switch to all-ram in there
; find slot currently set in page 1
; returns slot in reg a using FxxxSSPP format (see enaslt)
find_rom:
- in a,(0xa8)
+ in a,(SLOT_SEL)
rrca
rrca
and #3
; find slot currently set in page 3
; returns slot in reg a using FxxxSSPP format (see enaslt)
find_ram:
- in a,(0xa8)
+ in a,(SLOT_SEL)
rlca
rlca
and #3
enaslt:
call selprm ; calculate bit pattern and mask code
jp m, eneslt ; if expanded set secondary first
- in a,(0xa8)
+ in a,(SLOT_SEL)
and c
or b
- out (0xa8),a ; set primary slot
+ out (SLOT_SEL),a ; set primary slot
ret
eneslt:
push hl
pop af
push af
ld d,a
- in a,(0xa8)
+ in a,(SLOT_SEL)
ld b,a
and #0x3F
or c
- out (0xa8),a ; set bank 3 to target slot
+ out (SLOT_SEL),a ; set bank 3 to target slot
ld a,d
rrca
rrca
ld a,e
cpl
ld h,a
- ld a,(0xffff) ; read and update secondary slot register
+ ld a,(SUBSLOT_SEL) ; read and update secondary slot register
cpl
ld l,a
and h ; strip off old bits
or d ; add new bits
- ld (0xffff),a
+ ld (SUBSLOT_SEL),a
ld a,b
- out (0xa8),a ; restore status
+ out (SLOT_SEL),a ; restore status
pop af
and #3
ret
RAM_PAGE1 .equ 0xFD
RAM_PAGE2 .equ 0xFE
RAM_PAGE3 .equ 0xFF
+
+;
+; ASCII 8Kb Mapper addresses
+;
+ASCII8_PAGE0_BASE .equ 0x4000
+ASCII8_PAGE1_BASE .equ 0x6000
+ASCII8_PAGE2_BASE .equ 0x8000
+ASCII8_PAGE3_BASE .equ 0xA000
+
+ASCII8_ROM_PAGE0 .equ 0x6000
+ASCII8_ROM_PAGE1 .equ 0x6800
+ASCII8_ROM_PAGE2 .equ 0x7000
+ASCII8_ROM_PAGE3 .equ 0x7800
+
+;
+; BIOS machine info addresses
+;
+BIOS_VERSION1 .equ 0x002B
+BIOS_VERSION2 .equ 0x002C
+BIOS_MACHINE_TYPE .equ 0x002D
+BIOS_VDP_IOPORT .equ 0x0006
+
+;
+; OpenMSX Debug ports
+;
+OPENMSX_DEBUG1 .equ 0x2E
+OPENMSX_DEBUG2 .equ 0x2F
+
+
public / FUZIX.git / commitdiff