Documentation/m68k/README.buddha

   1
   2 The Amiga Buddha and Catweasel IDE Driver (part of ide.c) was written by
   3 Geert Uytterhoeven based on the following specifications:
   4
   5 ------------------------------------------------------------------------
   6
   7 Register map of the Buddha IDE controller and the
   8 Buddha-part of the Catweasel Zorro-II version
   9
  10 The Autoconfiguration has been implemented just as Commodore
  11 described  in  their  manuals, no tricks have been used (for
  12 example leaving some address lines out of the equations...).
  13 If you want to configure the board yourself (for example let
  14 a  Linux  kernel  configure the card), look at the Commodore
  15 Docs.  Reading the nibbles should give this information:
  16
  17 Vendor number: 4626 ($1212)
  18 product number: 0 (42 for Catweasel Z-II)
  19 Serial number: 0
  20 Rom-vector: $1000
  21
  22 The  card  should be a Z-II board, size 64K, not for freemem
  23 list, Rom-Vektor is valid, no second Autoconfig-board on the
  24 same card, no space preference, supports "Shutup_forever".
  25
  26 Setting  the  base address should be done in two steps, just
  27 as  the Amiga Kickstart does:  The lower nibble of the 8-Bit
  28 address is written to $4a, then the whole Byte is written to
  29 $48, while it doesn't matter how often you're writing to $4a
  30 as  long as $48 is not touched.  After $48 has been written,
  31 the  whole card disappears from $e8 and is mapped to the new
  32 address just written.  Make sure $4a is written before $48,
  33 otherwise your chance is only 1:16 to find the board :-).
  34
  35 The local memory-map is even active when mapped to $e8:
  36
  37 $0-$7e          Autokonfig-space, see Z-II docs.
  38
  39 $80-$7fd        reserved
  40
  41 $7fe            Speed-select Register: Read & Write
  42                 (description see further down)
  43
  44 $800-$8ff       IDE-Select 0 (Port 0, Register set 0)
  45
  46 $900-$9ff       IDE-Select 1 (Port 0, Register set 1)
  47
  48 $a00-$aff       IDE-Select 2 (Port 1, Register set 0)
  49
  50 $b00-$bff       IDE-Select 3 (Port 1, Register set 1)
  51
  52 $c00-$cff       IDE-Select 4 (Port 2, Register set 0,
  53                           Catweasel only!)
  54
  55 $d00-$dff       IDE-Select 5 (Port 3, Register set 1,
  56                               Catweasel only!)
  57
  58 $e00-$eff       local expansion port, on Catweasel Z-II the
  59                 Catweasel registers are also mapped here.
  60                 Never touch, use multidisk.device!
  61
  62 $f00            read only, Byte-access: Bit 7 shows the
  63                 level of the IRQ-line of IDE port 0.
  64
  65 $f01-$f3f       mirror of $f00
  66
  67 $f40            read only, Byte-access: Bit 7 shows the
  68                 level of the IRQ-line of IDE port 1.
  69
  70 $f41-$f7f       mirror of $f40
  71
  72 $f80            read only, Byte-access: Bit 7 shows the
  73                 level of the IRQ-line of IDE port 2.
  74                 (Catweasel only!)
  75
  76 $f81-$fbf       mirror of $f80
  77
  78 $fc0            write-only: Writing any value to this
  79                 register enables IRQs to be passed from the
  80                 IDE ports to the Zorro bus. This mechanism
  81                 has been implemented to be compatible with
  82                 harddisks that are either defective or have
  83                 a buggy firmware and pull the IRQ line up
  84                 while starting up. If interrupts would
  85                 always be passed to the bus, the computer
  86                 might not start up. Once enabled, this flag
  87                 can not be disabled again. The level of the
  88                 flag can not be determined by software
  89                 (what for? Write to me if it's necessary!).
  90
  91 $fc1-$fff       mirror of $fc0
  92
  93 $1000-$ffff     Buddha-Rom with offset $1000 in the rom
  94                 chip. The addresses $0 to $fff of the rom
  95                 chip cannot be read. Rom is Byte-wide and
  96                 mapped to even addresses.
  97
  98 The  IDE ports issue an INT2.  You can read the level of the
  99 IRQ-lines  of  the  IDE-ports by reading from the three (two
 100 for  Buddha-only)  registers  $f00, $f40 and $f80.  This way
 101 more  than one I/O request can be handled and you can easily
 102 determine  what  driver  has  to serve the INT2.  Buddha and
 103 Catweasel  expansion  boards  can issue an INT6.  A separate
 104 memory  map  is available for the I/O module and the sysop's
 105 I/O module.
 106
 107 The IDE ports are fed by the address lines A2 to A4, just as
 108 the  Amiga  1200  and  Amiga  4000  IDE ports are.  This way
 109 existing  drivers  can be easily ported to Buddha.  A move.l
 110 polls  two  words  out of the same address of IDE port since
 111 every  word  is  mirrored  once.  movem is not possible, but
 112 it's  not  necessary  either,  because  you can only speedup
 113 68000  systems  with  this  technique.   A 68020 system with
 114 fastmem is faster with move.l.
 115
 116 If you're using the mirrored registers of the IDE-ports with
 117 A6=1,  the Buddha doesn't care about the speed that you have
 118 selected  in  the  speed  register (see further down).  With
 119 A6=1  (for example $840 for port 0, register set 0), a 780ns
 120 access  is being made.  These registers should be used for a
 121 command   access   to  the  harddisk/CD-Rom,  since  command
 122 accesses  are Byte-wide and have to be made slower according
 123 to the ATA-X3T9 manual.
 124
 125 Now  for the speed-register:  The register is byte-wide, and
 126 only  the  upper  three  bits are used (Bits 7 to 5).  Bit 4
 127 must  always  be set to 1 to be compatible with later Buddha
 128 versions  (if  I'll  ever  update this one).  I presume that
 129 I'll  never use the lower four bits, but they have to be set
 130 to 1 by definition.
 131   The  values in this table have to be shifted 5 bits to the
 132 left and or'd with $1f (this sets the lower 5 bits).
 133
 134 All  the timings have in common:  Select and IOR/IOW rise at
 135 the  same  time.   IOR  and  IOW have a propagation delay of
 136 about  30ns  to  the clocks on the Zorro bus, that's why the
 137 values  are no multiple of 71.  One clock-cycle is 71ns long
 138 (exactly 70,5 at 14,18 Mhz on PAL systems).
 139
 140 value 0 (Default after reset)
 141
 142 497ns Select (7 clock cycles) , IOR/IOW after 172ns (2 clock cycles)
 143 (same timing as the Amiga 1200 does on it's IDE port without
 144 accelerator card)
 145
 146 value 1
 147
 148 639ns Select (9 clock cycles), IOR/IOW after 243ns (3 clock cycles)
 149
 150 value 2
 151
 152 781ns Select (11 clock cycles), IOR/IOW after 314ns (4 clock cycles)
 153
 154 value 3
 155
 156 355ns Select (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
 157
 158 value 4
 159
 160 355ns Select (5 clock cycles), IOR/IOW after 172ns (2 clock cycles)
 161
 162 value 5
 163
 164 355ns Select (5 clock cycles), IOR/IOW after 243ns (3 clock cycles)
 165
 166 value 6
 167
 168 1065ns Select (15 clock cycles), IOR/IOW after 314ns (4 clock cycles)
 169
 170 value 7
 171
 172 355ns Select, (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
 173
 174 When accessing IDE registers with A6=1 (for example $84x),
 175 the timing will always be mode 0 8-bit compatible, no matter
 176 what you have selected in the speed register:
 177
 178 781ns select, IOR/IOW after 4 clock cycles (=314ns) aktive.
 179
 180 All  the  timings with a very short select-signal (the 355ns
 181 fast  accesses)  depend  on the accelerator card used in the
 182 system:  Sometimes two more clock cycles are inserted by the
 183 bus  interface,  making  the  whole access 497ns long.  This
 184 doesn't  affect  the  reliability  of the controller nor the
 185 performance  of  the  card,  since  this doesn't happen very
 186 often.
 187
 188 All  the  timings  are  calculated  and  only  confirmed  by
 189 measurements  that allowed me to count the clock cycles.  If
 190 the  system  is clocked by an oscillator other than 28,37516
 191 Mhz  (for  example  the  NTSC-frequency  28,63636 Mhz), each
 192 clock  cycle is shortened to a bit less than 70ns (not worth
 193 mentioning).   You  could think of a small performance boost
 194 by  overclocking  the  system,  but  you would either need a
 195 multisync  monitor,  or  a  graphics card, and your internal
 196 diskdrive would go crazy, that's why you shouldn't tune your
 197 Amiga this way.
 198
 199 Giving  you  the  possibility  to  write  software  that  is
 200 compatible  with both the Buddha and the Catweasel Z-II, The
 201 Buddha  acts  just  like  a  Catweasel  Z-II  with no device
 202 connected  to  the  third  IDE-port.   The IRQ-register $f80
 203 always  shows a "no IRQ here" on the Buddha, and accesses to
 204 the  third  IDE  port  are  going into data's Nirwana on the
 205 Buddha.
 206
 207                             Jens Schönfeld february 19th, 1997
 208                                         updated may 27th, 1997
 209                              eMail: sysop@nostlgic.tng.oche.de
 210