linux/Documentation/m68k/README.buddha
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   1
   2The Amiga Buddha and Catweasel IDE Driver (part of ide.c) was written by
   3Geert Uytterhoeven based on the following specifications:
   4
   5------------------------------------------------------------------------
   6
   7Register map of the Buddha IDE controller and the
   8Buddha-part of the Catweasel Zorro-II version
   9
  10The Autoconfiguration has been implemented just as Commodore
  11described  in  their  manuals, no tricks have been used (for
  12example leaving some address lines out of the equations...).
  13If you want to configure the board yourself (for example let
  14a  Linux  kernel  configure the card), look at the Commodore
  15Docs.  Reading the nibbles should give this information:
  16
  17Vendor number: 4626 ($1212)
  18product number: 0 (42 for Catweasel Z-II)
  19Serial number: 0
  20Rom-vector: $1000
  21
  22The  card  should be a Z-II board, size 64K, not for freemem
  23list, Rom-Vektor is valid, no second Autoconfig-board on the
  24same card, no space preference, supports "Shutup_forever".
  25
  26Setting  the  base address should be done in two steps, just
  27as  the Amiga Kickstart does:  The lower nibble of the 8-Bit
  28address 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
  30as  long as $48 is not touched.  After $48 has been written,
  31the  whole card disappears from $e8 and is mapped to the new
  32address just written.  Make sure $4a is written before $48,
  33otherwise your chance is only 1:16 to find the board :-).
  34
  35The 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
  98The  IDE ports issue an INT2.  You can read the level of the
  99IRQ-lines  of  the  IDE-ports by reading from the three (two
 100for  Buddha-only)  registers  $f00, $f40 and $f80.  This way
 101more  than one I/O request can be handled and you can easily
 102determine  what  driver  has  to serve the INT2.  Buddha and
 103Catweasel  expansion  boards  can issue an INT6.  A separate
 104memory  map  is available for the I/O module and the sysop's
 105I/O module.
 106
 107The IDE ports are fed by the address lines A2 to A4, just as
 108the  Amiga  1200  and  Amiga  4000  IDE ports are.  This way
 109existing  drivers  can be easily ported to Buddha.  A move.l
 110polls  two  words  out of the same address of IDE port since
 111every  word  is  mirrored  once.  movem is not possible, but
 112it's  not  necessary  either,  because  you can only speedup
 11368000  systems  with  this  technique.   A 68020 system with
 114fastmem is faster with move.l.
 115
 116If you're using the mirrored registers of the IDE-ports with
 117A6=1,  the Buddha doesn't care about the speed that you have
 118selected  in  the  speed  register (see further down).  With
 119A6=1  (for example $840 for port 0, register set 0), a 780ns
 120access  is being made.  These registers should be used for a
 121command   access   to  the  harddisk/CD-Rom,  since  command
 122accesses  are Byte-wide and have to be made slower according
 123to the ATA-X3T9 manual.
 124
 125Now  for the speed-register:  The register is byte-wide, and
 126only  the  upper  three  bits are used (Bits 7 to 5).  Bit 4
 127must  always  be set to 1 to be compatible with later Buddha
 128versions  (if  I'll  ever  update this one).  I presume that
 129I'll  never use the lower four bits, but they have to be set
 130to 1 by definition.
 131  The  values in this table have to be shifted 5 bits to the
 132left and or'd with $1f (this sets the lower 5 bits).
 133
 134All  the timings have in common:  Select and IOR/IOW rise at
 135the  same  time.   IOR  and  IOW have a propagation delay of
 136about  30ns  to  the clocks on the Zorro bus, that's why the
 137values  are no multiple of 71.  One clock-cycle is 71ns long
 138(exactly 70,5 at 14,18 Mhz on PAL systems).
 139
 140value 0 (Default after reset)
 141
 142497ns 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
 144accelerator card)
 145
 146value 1
 147
 148639ns Select (9 clock cycles), IOR/IOW after 243ns (3 clock cycles)
 149
 150value 2
 151
 152781ns Select (11 clock cycles), IOR/IOW after 314ns (4 clock cycles)
 153
 154value 3
 155
 156355ns Select (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
 157
 158value 4
 159
 160355ns Select (5 clock cycles), IOR/IOW after 172ns (2 clock cycles)
 161
 162value 5
 163
 164355ns Select (5 clock cycles), IOR/IOW after 243ns (3 clock cycles)
 165
 166value 6
 167
 1681065ns Select (15 clock cycles), IOR/IOW after 314ns (4 clock cycles)
 169
 170value 7
 171
 172355ns Select, (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
 173
 174When accessing IDE registers with A6=1 (for example $84x),
 175the timing will always be mode 0 8-bit compatible, no matter
 176what you have selected in the speed register:
 177
 178781ns select, IOR/IOW after 4 clock cycles (=314ns) aktive. 
 179
 180All  the  timings with a very short select-signal (the 355ns
 181fast  accesses)  depend  on the accelerator card used in the
 182system:  Sometimes two more clock cycles are inserted by the
 183bus  interface,  making  the  whole access 497ns long.  This
 184doesn't  affect  the  reliability  of the controller nor the
 185performance  of  the  card,  since  this doesn't happen very
 186often.
 187
 188All  the  timings  are  calculated  and  only  confirmed  by
 189measurements  that allowed me to count the clock cycles.  If
 190the  system  is clocked by an oscillator other than 28,37516
 191Mhz  (for  example  the  NTSC-frequency  28,63636 Mhz), each
 192clock  cycle is shortened to a bit less than 70ns (not worth
 193mentioning).   You  could think of a small performance boost
 194by  overclocking  the  system,  but  you would either need a
 195multisync  monitor,  or  a  graphics card, and your internal
 196diskdrive would go crazy, that's why you shouldn't tune your
 197Amiga this way.
 198
 199Giving  you  the  possibility  to  write  software  that  is
 200compatible  with both the Buddha and the Catweasel Z-II, The
 201Buddha  acts  just  like  a  Catweasel  Z-II  with no device
 202connected  to  the  third  IDE-port.   The IRQ-register $f80
 203always  shows a "no IRQ here" on the Buddha, and accesses to
 204the  third  IDE  port  are  going into data's Nirwana on the
 205Buddha.
 206
 207                            Jens Schönfeld february 19th, 1997
 208                                        updated may 27th, 1997
 209                             eMail: sysop@nostlgic.tng.oche.de
 210
 211
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