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| README.buddha | ||
The Amiga Buddha and Catweasel IDE Driver (part of ide.c) was written by
Geert Uytterhoeven based on the following specifications:
------------------------------------------------------------------------
Register map of the Buddha IDE controller and the
Buddha-part of the Catweasel Zorro-II version
The Autoconfiguration has been implemented just as Commodore
described in their manuals, no tricks have been used (for
example leaving some address lines out of the equations...).
If you want to configure the board yourself (for example let
a Linux kernel configure the card), look at the Commodore
Docs. Reading the nibbles should give this information:
Vendor number: 4626 ($1212)
product number: 0 (42 for Catweasel Z-II)
Serial number: 0
Rom-vector: $1000
The card should be a Z-II board, size 64K, not for freemem
list, Rom-Vektor is valid, no second Autoconfig-board on the
same card, no space preference, supports "Shutup_forever".
Setting the base address should be done in two steps, just
as the Amiga Kickstart does: The lower nibble of the 8-Bit
address is written to $4a, then the whole Byte is written to
$48, while it doesn't matter how often you're writing to $4a
as long as $48 is not touched. After $48 has been written,
the whole card disappears from $e8 and is mapped to the new
address just written. Make sure $4a is written before $48,
otherwise your chance is only 1:16 to find the board :-).
The local memory-map is even active when mapped to $e8:
$0-$7e Autokonfig-space, see Z-II docs.
$80-$7fd reserved
$7fe Speed-select Register: Read & Write
(description see further down)
$800-$8ff IDE-Select 0 (Port 0, Register set 0)
$900-$9ff IDE-Select 1 (Port 0, Register set 1)
$a00-$aff IDE-Select 2 (Port 1, Register set 0)
$b00-$bff IDE-Select 3 (Port 1, Register set 1)
$c00-$cff IDE-Select 4 (Port 2, Register set 0,
Catweasel only!)
$d00-$dff IDE-Select 5 (Port 3, Register set 1,
Catweasel only!)
$e00-$eff local expansion port, on Catweasel Z-II the
Catweasel registers are also mapped here.
Never touch, use multidisk.device!
$f00 read only, Byte-access: Bit 7 shows the
level of the IRQ-line of IDE port 0.
$f01-$f3f mirror of $f00
$f40 read only, Byte-access: Bit 7 shows the
level of the IRQ-line of IDE port 1.
$f41-$f7f mirror of $f40
$f80 read only, Byte-access: Bit 7 shows the
level of the IRQ-line of IDE port 2.
(Catweasel only!)
$f81-$fbf mirror of $f80
$fc0 write-only: Writing any value to this
register enables IRQs to be passed from the
IDE ports to the Zorro bus. This mechanism
has been implemented to be compatible with
harddisks that are either defective or have
a buggy firmware and pull the IRQ line up
while starting up. If interrupts would
always be passed to the bus, the computer
might not start up. Once enabled, this flag
can not be disabled again. The level of the
flag can not be determined by software
(what for? Write to me if it's necessary!).
$fc1-$fff mirror of $fc0
$1000-$ffff Buddha-Rom with offset $1000 in the rom
chip. The addresses $0 to $fff of the rom
chip cannot be read. Rom is Byte-wide and
mapped to even addresses.
The IDE ports issue an INT2. You can read the level of the
IRQ-lines of the IDE-ports by reading from the three (two
for Buddha-only) registers $f00, $f40 and $f80. This way
more than one I/O request can be handled and you can easily
determine what driver has to serve the INT2. Buddha and
Catweasel expansion boards can issue an INT6. A separate
memory map is available for the I/O module and the sysop's
I/O module.
The IDE ports are fed by the address lines A2 to A4, just as
the Amiga 1200 and Amiga 4000 IDE ports are. This way
existing drivers can be easily ported to Buddha. A move.l
polls two words out of the same address of IDE port since
every word is mirrored once. movem is not possible, but
it's not necessary either, because you can only speedup
68000 systems with this technique. A 68020 system with
fastmem is faster with move.l.
If you're using the mirrored registers of the IDE-ports with
A6=1, the Buddha doesn't care about the speed that you have
selected in the speed register (see further down). With
A6=1 (for example $840 for port 0, register set 0), a 780ns
access is being made. These registers should be used for a
command access to the harddisk/CD-Rom, since command
accesses are Byte-wide and have to be made slower according
to the ATA-X3T9 manual.
Now for the speed-register: The register is byte-wide, and
only the upper three bits are used (Bits 7 to 5). Bit 4
must always be set to 1 to be compatible with later Buddha
versions (if I'll ever update this one). I presume that
I'll never use the lower four bits, but they have to be set
to 1 by definition.
The values in this table have to be shifted 5 bits to the
left and or'd with $1f (this sets the lower 5 bits).
All the timings have in common: Select and IOR/IOW rise at
the same time. IOR and IOW have a propagation delay of
about 30ns to the clocks on the Zorro bus, that's why the
values are no multiple of 71. One clock-cycle is 71ns long
(exactly 70,5 at 14,18 Mhz on PAL systems).
value 0 (Default after reset)
497ns Select (7 clock cycles) , IOR/IOW after 172ns (2 clock cycles)
(same timing as the Amiga 1200 does on it's IDE port without
accelerator card)
value 1
639ns Select (9 clock cycles), IOR/IOW after 243ns (3 clock cycles)
value 2
781ns Select (11 clock cycles), IOR/IOW after 314ns (4 clock cycles)
value 3
355ns Select (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
value 4
355ns Select (5 clock cycles), IOR/IOW after 172ns (2 clock cycles)
value 5
355ns Select (5 clock cycles), IOR/IOW after 243ns (3 clock cycles)
value 6
1065ns Select (15 clock cycles), IOR/IOW after 314ns (4 clock cycles)
value 7
355ns Select, (5 clock cycles), IOR/IOW after 101ns (1 clock cycle)
When accessing IDE registers with A6=1 (for example $84x),
the timing will always be mode 0 8-bit compatible, no matter
what you have selected in the speed register:
781ns select, IOR/IOW after 4 clock cycles (=314ns) aktive.
All the timings with a very short select-signal (the 355ns
fast accesses) depend on the accelerator card used in the
system: Sometimes two more clock cycles are inserted by the
bus interface, making the whole access 497ns long. This
doesn't affect the reliability of the controller nor the
performance of the card, since this doesn't happen very
often.
All the timings are calculated and only confirmed by
measurements that allowed me to count the clock cycles. If
the system is clocked by an oscillator other than 28,37516
Mhz (for example the NTSC-frequency 28,63636 Mhz), each
clock cycle is shortened to a bit less than 70ns (not worth
mentioning). You could think of a small performance boost
by overclocking the system, but you would either need a
multisync monitor, or a graphics card, and your internal
diskdrive would go crazy, that's why you shouldn't tune your
Amiga this way.
Giving you the possibility to write software that is
compatible with both the Buddha and the Catweasel Z-II, The
Buddha acts just like a Catweasel Z-II with no device
connected to the third IDE-port. The IRQ-register $f80
always shows a "no IRQ here" on the Buddha, and accesses to
the third IDE port are going into data's Nirwana on the
Buddha.
Jens Schönfeld february 19th, 1997
updated may 27th, 1997
eMail: sysop@nostlgic.tng.oche.de