diff options
Diffstat (limited to 'Documentation/arch/m68k/buddha-driver.rst')
| -rw-r--r-- | Documentation/arch/m68k/buddha-driver.rst | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/Documentation/arch/m68k/buddha-driver.rst b/Documentation/arch/m68k/buddha-driver.rst new file mode 100644 index 000000000000..20e401413991 --- /dev/null +++ b/Documentation/arch/m68k/buddha-driver.rst @@ -0,0 +1,209 @@ +===================================== +Amiga Buddha and Catweasel IDE Driver +===================================== + +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 |