I checked now with MS-DOS and issuing a simple "DIR D:\" command with
a power cycled disk:
Command: C4h (Read Multiple)
-> 51h, 51h -> 04h
Command: 10h (Obsolete???)
-> 50h, 50h -> 04h
Command: 91h (Initialize Drive Parameters)
-> d0h, d0h, d0h, .... 50h
Command: C6h (Set Multiple Mode)
-> 50h
Command: C4h (Read Multiple)
-> 58h
The first C4h Command returns the same error, but
after this it seems like the drive is "initialized"
and then the 2nd C4 command afterwards works! Great.
I guess C6h is only needed because read multiple is
used, so I probably have to do only the 10h and
91h stuff... just need to find out more about it.
Does anyone know what command 10h is? The documentation
I have only states "obsolete".
Oliver Lehmann <lehm...@ans-netz.de> wrote:
OK,
detatching the power cord of the disk from my PC while
running FreeBSD and reattaching it also brings up error
code 4 on the next access. This does not happen with
other drives. So it must be some sort of initialisation
the OS or BIOS does which readies up the drive.
Oliver Lehmann <lehm...@ans-netz.de> wrote:
OK, I just got my Logic Analysator and traced the
communication on my PC while forcing it to do PIO
instead of DMA.
I then changed my AVR code to do the exact same
commands and nearly the same timings and... nothing
changed - the drive still responds with error code
0x04 after the read sector 0x20 command is issued.
On the PC:
I noticed a time frame of 115,230ns between the
0x20 Command and the first alternate status register
read. during that time, INTRQ goes high so the drive
"is done" and wants the host to interact with it
again. IORDY is the whole time high from the host.
The status read is 0x58 on the PC.
On the AVR:
IORDY is the whole time low (it is not connected),
INTRQ stays low the whole time, and the first status
read back is 0xD0 for a long time and then it goes to
0xD1 and then 0x59.
Things I plan to try next:
- power down the drive on the pc, power it up and then
try to access sector 1 again and see what happens.
Maybe some magic "initialization" is done on bootup
what I don't do.
- make IORDY high on my AVR too
