avrcpm/z80/bios.asm

   1 ;    CP/M BIOS for avrcpm
   2 ;    Copyright (C) 2010 Sprite_tm
   3 ;
   4 ;    This program is free software: you can redistribute it and/or modify
   5 ;    it under the terms of the GNU General Public License as published by
   6 ;    the Free Software Foundation, either version 3 of the License, or
   7 ;    (at your option) any later version.
   8 ;
   9 ;    This program is distributed in the hope that it will be useful,
  10 ;    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 ;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 ;    GNU General Public License for more details.
  13 ;
  14 ;    You should have received a copy of the GNU General Public License
  15 ;    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 msize:  equ     62      ;size of available RAM in k
  18
  19 bias:   equ     (msize-20) * 1024
  20 ccp:    equ     $3400+bias      ;base of cpm ccp
  21 bdos:   equ     ccp+$806        ;base of bdos
  22 bios:   equ     ccp+$1600       ;base of bios
  23 cdisk:  equ     $0004           ;current disk number (0 ... 15)
  24 iobyte: equ     $0003           ;intel iobyte
  25 buff:   equ     $0080           ;default buffer address
  26 retry:  equ     3               ;max retries on disk i/o before error
  27
  28 cr:     equ     13
  29 lf:     equ     10
  30
  31         org     bios
  32 nsects: equ     ($-ccp)/128     ;warm start sector count
  33
  34         jp boot
  35 wboote:
  36         jp wboot
  37         jp const
  38         jp conin
  39         jp conout
  40         jp list
  41         jp punch
  42         jp reader
  43         jp home
  44         jp seldsk
  45         jp settrk
  46         jp setsec
  47         jp setdma
  48         jp read
  49         jp write
  50         jp listst
  51         jp sectran
  52
  53 signon:
  54         db      cr,lf
  55         db      msize/10+'0'
  56         db      msize - (msize/10)*10 + '0'     ;modulo doesn't work?
  57         db      "k cp/m vers 2.2"
  58         db      cr,lf,0
  59
  60 boot:
  61         ld      sp,buff
  62         ld      hl,signon
  63         call    prmsg
  64         xor     a
  65         ld      (iobyte),a
  66         ld      (cdisk),a
  67         jp      gocpm
  68
  69 wboot:  ;re-load CP/M
  70         ld      sp,buff
  71         ld      c,0
  72         call    seldsk
  73         call    home
  74         ld      b,nsects
  75         ld      c,0             ;track
  76         ld      d,1             ;sektor (0 based)
  77         ld      hl,ccp
  78 load1:
  79         push    bc
  80         push    de
  81         push    hl
  82         ld      c,d
  83         call    setsec
  84         pop     bc
  85         push    bc
  86         call    setdma
  87         call    read
  88         cp      0               ;read error?
  89         jp      nz,wboot
  90
  91         pop     hl
  92         ld      de,128
  93         add     hl,de
  94         pop     de
  95         pop     bc
  96         dec     b
  97         jp      z,gocpm
  98
  99         inc     d
 100         ld      a,d
 101         cp      26              ;if sector >= 26 then change tracks
 102         jp      c,load1
 103
 104         ld      d,0
 105         inc     c
 106         push    bc
 107         push    de
 108         push    hl
 109         call    settrk
 110         pop     hl
 111         pop     de
 112         pop     bc
 113         jp      load1
 114
 115 gocpm:
 116         ld      a,0c3h
 117         ld      (0),a
 118         ld      hl,wboote
 119         ld      (1),hl
 120         ld      (5),a
 121         ld      hl,bdos
 122         ld      (6),hl
 123
 124         ld      bc,buff
 125         call    setdma
 126         ld      a,(cdisk)
 127         ld      c,a
 128         jp      ccp
 129
 130 const:
 131         in a,(0)
 132         ret
 133
 134 conin:
 135         in a,(0)
 136         cp $ff
 137         jp nz,conin
 138
 139         in a,(1)
 140         ret
 141
 142 conout:
 143         ld a,c
 144         out (2),a
 145         ret
 146
 147 list:
 148         ret
 149
 150 listst:
 151         ld a,0
 152         ret
 153
 154 punch:
 155         ret
 156
 157 reader:
 158         ld a,$1F
 159         ret
 160
 161 home:
 162         push af
 163         ld a,0
 164         out (16),a
 165         pop af
 166         ret
 167
 168 seldsk:
 169         push af
 170         ld a,c
 171         cp 0
 172         jp nz,seldsk_na
 173         ld hl,dph
 174         pop af
 175         ret
 176 seldsk_na:
 177         ld hl,0
 178         pop af
 179         ret
 180
 181 settrk:
 182         push af
 183         ld a,c
 184         out (16),a
 185         pop af
 186         ret
 187
 188 setsec:
 189         push af
 190         ld a,c
 191         out (18),a
 192         pop af
 193         ret
 194
 195 setdma:
 196         push af
 197         ld a,c
 198         out (20),a
 199         ld a,b
 200         out (21),a
 201         pop af
 202         ret
 203
 204 read:
 205         ld a,1
 206         out (22),a
 207         ld a,0
 208         ret
 209
 210 write:
 211         ld a,2
 212         out (22),a
 213         ld a,0
 214         ret
 215
 216 sectran:
 217         ;translate sector bc using table at de, res into hl
 218         ;not implemented :)
 219         ld h,b
 220         ld l,c
 221         ret
 222
 223 prmsg:
 224         ld      a,(hl)
 225         or      a
 226         ret     z
 227         push    hl
 228         ld      c,a
 229         call    conout
 230         pop     hl
 231         inc     hl
 232         jp      prmsg
 233
 234
 235 ;Disk Parameter Header
 236 dph:
 237         dw trans ;XLT: Address of translation table
 238         dw 0 ;000: Scratchpad
 239         dw 0 ;000: Scratchpad
 240         dw 0 ;000: Scratchpad
 241         dw dirbuf ;DIRBUF: Address of a dirbuff scratchpad
 242         dw dpb ;DPB: Address of a disk parameter block
 243         dw chk ;CSV: Address of scratchpad area for changed disks
 244         dw all ;ALV: Address of an allocation info sratchpad
 245
 246 dpb:
 247         dw 26 ;SPT: sectors per track
 248         db 3 ;BSH: data allocation block shift factor
 249         db 7 ;BLM: Data Allocation Mask
 250         db 0 ;Extent mask
 251         dw 242 ;DSM: Disk storage capacity
 252         dw 63 ;DRM, no of directory entries
 253         db 192 ;AL0
 254         db 0 ;AL1
 255         dw 16 ;CKS, size of dir check vector
 256         dw 2 ;OFF, no of reserved tracks
 257
 258 trans:
 259         db 0,1,2,3,4,5,6,7,8,9
 260         db 10,11,12,13,14,15,16,17,18,19
 261         db 19,20,21,22,23,24,25,26
 262
 263 dirbuf:
 264         ds 128
 265
 266 chk:
 267         ds 16
 268
 269 all:
 270         ds 31
 271
 272 end