;
; TRS80 bootblock (256 bytes)
;
-; FIXME rewrite for model 1
+;
+; We load from 0x4300-0xFFFF into common and bank 0, then switch
+; to loading from 0x8000-0xFFFF in bank1. That takes 320 sectors
+; at 10 sectors per track so 32 tracks of those available (which may
+; only be 35). Track 0 holds the boot block.
+;
+; We could optimize this once we have the layout better planned so we
+; load less empty space. On the other hand we've only got 256 bytes
+; of space to play in.
;
.area BOOT (ABS)
-.org 0x000
-start:
- ld a, #0x86 ; kernel map, 80 column, no remap
- out (0x84), a ; video page 1
- ld a, #0x50 ; 80 column, sound, altchars off,
- ; ext I/O on , 4MHz
- out (0xEC), a
- ld hl, #0x4300
- ld de, #0x0
- ld bc, #256
- ldir
- jp go
+.org 0x4200
+
;
-; Assume the boot ROM left us on track 0 and motor on
+; The 1791 is memory mapped
;
-floppy_read:
- ld bc, #0x81F4 ; select drive
- out (c), b
- out (0xF2), a ; sector please
- ld a, #0x80 ; READ
- out (0xF0), a
- ld b, #100
-l1: djnz l1
- ld de, #0x8116
- ld bc, #0xF3
-flopin: in a, (0xF0)
- and e
- jr z, flopin
- ini
- ld a, d
-flopind:
- out (0xF4), a
- ini
- jr nz, flopind
-flopstat:
- in a, (0xF0)
- and #0x19
- bit 0, a
- jr nz, flopstat
- or a
- ret z
- ld de, #0xF850
- call prints
- .ascii 'Read\0'
-fail: jr fail
+FDCREG .equ 0x37EC
+FDCTRK .equ 0x37ED
+FDCSEC .equ 0x37EE
+FDCDATA .equ 0x37EF
;
-go:
- ld sp, #0xEE00 ; temp stackpointer
-
- ; load the 6845 parameters
- ld hl, #_ctc6845 ; reverse order
- ld bc, #0x0F88
-ctcloop: out (c), b ; select register
- ld a, (hl)
- out (0x89), a ; output data
- dec hl
- djnz ctcloop
+; Drive select is also more complicated than other models
+;
+LATCHD0 .equ 0x37E1 ; also drive select
+LATCHD1 .equ 0x37E3
+LATCHD2 .equ 0x37E5
+LATCHD3 .equ 0x37E7
- ; clear screen
- ld hl, #0xF800
- ld de, #0xF801
- ld bc, #0x07FF
- ld (hl), #' '
- ldir
- ld de, #0xF800
+start:
+ call 0x04C3 ; 64 columns
+ ; Stack is at 407D
+ ; Loader message
+ ld de, #0x3C00
call prints
- .ascii 'TRS80Load 0.2\0'
-
- ld hl, #0x0100
-;
+ .ascii 'TRS80Load 0.2m1\0'
+ out (0x43),a ; a is 0 on prints return
+ ld bc, #0x4300 ; page aligned buffer we read into
+ ld de, #FDCDATA ; data port
+ ld hl, #FDCREG ; command port
-lastsec: ld a, (tracknum)
+lastsec: ld a, #0 ; self modifying to save space
inc a
- ld (tracknum), a
- cp #40
- jr z, booted
- out (0xF3), a
- ld a, #0x18 ; seek
- out (0xF0), a
- ld b, #100
+ ld (lastsec+1), a ; track number... (start on 1)
+ cp #33
+ jp z, booted
+ ld (FDCTRK),a
+ ld (0x3CF0),a ; XX
+ ld (hl),#21 ; seek, lowest step speed
+ ld b, c ; 0x00 256 delays
cmd1: djnz cmd1
-cmdwait: in a, (0xF0)
- bit 0, a
+cmdwait: bit 0, (hl)
jr z, seekstat
- bit 7, a
+ bit 7, (hl)
jr z, cmdwait
seekstat:
- in a, (0xF0)
+ ld a,(hl)
and #0x18
bit 0, a
jr nz, seekstat
or a
jr z, secmove
- ld de, #0xF850
- call prints
+ call printse
.ascii 'seek\0'
bad: jr bad
secmove: xor a
dec a
- ld (secnum), a
+ ld (nextsec+1), a
nextsec:
- ld a, (secnum)
+ ld (0x3CF1),a ; XX
+ ld a, #255 ; self modifying sector count
inc a
- ld (secnum), a
- cp #18
+ ld (nextsec+1), a
+ cp #10
jr z, lastsec
- push hl
call floppy_read
+ push hl
+ ld h,#0x3D
+ ld l,b
+ inc (hl)
pop hl
- inc h
jr nextsec
-
-tracknum: .db 28 ; tracks 29-39 (50688 bytes)
-
- ; ctc6845 registers in reverse order
- .db 99
- .db 80
- .db 85
- .db 10
- .db 25
- .db 4
- .db 24
- .db 24
- .db 0
- .db 9
- .db 101
- .db 9
- .db 0
- .db 0
-secnum: .db 0 ; recycle last crc value as secnum so we fit 256 bytes
-_ctc6845: .db 0
+;
+; Assume the boot ROM left us on track 0 and motor on
+;
+floppy_read:
+ ld (FDCSEC), a ; sector please
+ ld a, #0x01 ; drive 0 select
+ ld (LATCHD0), a ; keep motor on
+ ld a, #0x8C ; READ
+ ld (hl), a
+ ld b, a ; 8C is an acceptable delay!
+l1: djnz l1
+flopin: bit 1,(hl)
+ jr z, flopin
+ ld a,(de)
+ ld (bc),a
+ inc c ; page aligned
+ jr nz,flopin
+ inc b ; correct bc for next call
+ jr nc, flopstat ; passed FFFF ?
+ ld b,#0x80 ; go back to 8000 and change bank
+ ld a,#1
+ out (0x43),a
+flopstat:
+ ld a, (hl)
+ and #0x19
+ rra ; test bit 0
+ jr nz, flopstat
+ or a ; safe even though we rotated right
+ ret z
+ call printse
+ .ascii 'Read\0'
+fail: jr fail
+printse:
+ ld de, #0x3850
prints:
pop hl
printsl:
jr printsl
out: jp (hl)
-booted: ld de, #0xF850
- call prints
+booted: call printse
.ascii 'Booting..\0'
-
-; OS starts on the following byte
+ jr 0x4300
public / FUZIX.git / commitdiff